Secret Agent "X" – The Complete Series, Volume 1

Silent, horrible as the crushing coils of a serpent were those unseen fingers that blotted out men’s lives. A criminal of satanic proportions had risen — the “Black Master,” whose victims fell with livid, hideous faces and protruding tongues that seemed a ghastly mockery of the fate they had suffered. Along this terrible murder trail Secret Agent “X” gambled with the Dice of Death.

Chapter I

WARNING prickles raced along Federal Detective Bill Scanlon’s spine. A hunch told him he was being followed. He was a little man grown gray in the service — gray hair, gray mustache, and thin, grayish features. He looked slight — almost weak. Yet, in the long years he’d worked for Uncle Sam, he’d built up a reputation for courage and ability that few men in the D.C.L. could equal.

He turned his head alertly, stared back, and something seemed to move behind him in the long shadow cast by the trunk of a leafless maple.

For a moment he stood uncertainly, then retraced his steps.

There was no fear on his face, but his eyes were watchful. He slid the flat bulk of an automatic out of his side pocket and held it against his thigh, moving forward cautiously like a man walking on eggshells.

He came close to the big maple, sidestepped around it — but no one was there.

A puff of night wind clattered branches overhead. They were sheathed with ice and made a dry rattle like skeleton fingers clicking together. Bill Scanlon stood waiting.

Then he relaxed. A cat with coal black fur and glowing green eyes spat at him and slunk away. It might have been an evil omen, but Scanlon wasn’t superstitious. He thought it was only the cat he had seen.

Pocketing his gun, he set off up the street again. There was someone on it he wanted to see — someone who might be a valuable witness in a mysterious murder and kidnapping in which the government was interested.

A shadow detached itself from the blackness of a house stoop opposite the maple. Slinking spiderlike, the shadow moved after Scanlon, stalking from tree to tree, hedge to hedge, and stoop to stoop, drawing closer — always closer.

Scanlon turned to stare again, but he saw nothing. The shadow was crouched as still as death. There was something deadly, something horrible, in the purposefulness with which it drew nearer.

Scanlon moved on. The person he wanted to interview lived on this block.

A twig covered with ice snapped behind him. He turned a third time, staring, his breath rising like steam in the cold night air.

Still no one was in sight, but the skin along Scanlon’s scalp began to tingle. He grasped the butt of his gun, holding it in his pocket, his finger crooked through the trigger guard.

On his left was a hedge of evergreens shielding the lawn of a darkened house. The evergreens were covered with hoarfrost. There was a gap between them that seemed as black as the cavernous opening in the front of a skull. Scanlon stared toward it for seconds.

Then the pupils of his eyes widened. He crouched, opened his lips as if to speak — but no words came.

Somewhere in the darkness behind the hedge there was faint, quick movement. It seemed no more than the blurring of a shadow against another shadow. No one appeared. No hand came into sight. But suddenly Scanlon uttered a hoarse, rasping gurgle and reached toward his throat.

His body jerked spasmodically. For a moment he gave the impression of a man dangling horribly at the end of a taut rope. His shadow writhed and leaped on the icy sidewalk beside him. He slipped, skidded, made choking sounds, his finger tightening involuntarily on the trigger of his automatic.

The gun belched flame in his pocket. It made a report that blasted the silence of the winter night. The bullet struck the icy pavement and whined away into the darkness.

Scanlon had both hands at his throat now. He appeared to be clawing invisible, horrible fingers away from his neck; appeared to be fighting a losing battle with some hideous unseen strangler who had held him in an unearthly grip.

But he wasn’t a man to give up easily. His struggles became more desperate, more frenzied. He tore at his coat, ripped open his collar with fingers as taut as talons. His shadow mimicked every movement he made, leaping like a dancer pirouetting to some mad, macabre rhythm.

Then at last he slipped and fell to the pavement, his face purpling, his eyes bulging out. He continued to writhe, but he made no sound now except the terrible wheezing of air fighting to escape through an aperture too small for it. The mottled, hideous purple of his skin deepened until his complexion had the hue of an overripe plum. Livid spots appeared on it where veins stood out. They seemed ready to burst sickeningly as blood pumped through them from his wildly laboring heart.

His movements grew slowly feebler. Then from his open mouth his tongue protruded grotesquely, horribly, as though he were mocking the unseen, silent thing that had struck him down.

ECHOES of the shot fired by his dying fingers whispered along the night-darkened street. A light flashed in a house diagonally across from the spot where he lay. A man came out on the porch, peered around, saw Scanlon’s body, and ran across the street to it.

For seconds the man stood bareheaded, staring down; then he turned quickly, his eyes dark with fright, and ran back into the house to the telephone.

Silence descended on the street again — a silence that was punctuated only by the skeleton clicking of the ice-coated branches. They seemed to be sounding a monotonous, macabre rhythm — a dirge of death.

The rhythm was interrupted at last by the wail of a police siren up the long street. Headlights flared on the icy pavements. A slim, green roadster shot into view. It was a radio cruiser come in response to the bareheaded man’s telephoned message to headquarters.

The cop at the wheel was leaning sidewise, staring out. He jerked the car’s nose toward the curb and brought it to a halt beside the body of Scanlon. He and his companion jumped out.

They bent down, opened Scanlon’s coat, and pulled papers from his pocket — then stared in surprise. The taller of the two cops spoke grimly.

“A Federal dick. Call headquarters quick. They’ll want to know about this.”

The other cop obeyed. He started at a run across the street, climbed the steps of the lighted house, and disappeared inside.

In twenty minutes the police cruiser at the curb was joined by a black headquarters’ car filled with detectives. It slid to a screeching stop. The men leaped out and crowded close around Scanlon, their breaths mingling in the icy air and their long overcoats making sprawled shadows on the pavement

They stared at Scanlon’s credentials and examined his body. Inspector John Burks, head of the homicide squad was among them — a tall man with snapping black eyes and jet-black eyebrows that contrasted sharply with his white hair. He began speaking in abrupt sentences.

“Strangled! Look at his face!”

A police sergeant flashed his light lower, then answered hoarsely, a note of fear in his voice.

“There ain’t no finger marks, chief. It’s like — like that woman who was killed last week, and those other guys — the taxi driver and the feller with him that they found in the vacant lot. Four of ’em murdered now — and all alike!”

Inspector Burks was silent for tense seconds. His thin face was working. His mouth was harsh. Four murders all alike! Four homicides as mysterious as they were horrible! Men strangled apparently by ghost fingers — their lives snuffed out by unseen hands. There had been no mark even on the white neck of the woman, the first victim. Yet her eyes, too, had been, staring and her tongue had protruded in that terrible mockery of death.

This was no ordinary murder case. It was uncanny, baffling, with the police already in a cul-de-sac from which there seemed to be no logical way out. A new and hideous crime wave was engulfing the city. Burks struck his clenched fist sharply against his palm.

“There’s a man I’d look for in this,” he grated. “A man who might do such things — the criminal who calls himself Secret Agent ‘X.’”

The sergeant bending over nodded somberly.

“Right, chief. It’s the kind of screwy job he might pull. But he’s a tough man to lay hold of. He never looks the same twice.”

“He’ll slip up,” said Burks harshly. “He’s almost done it a couple of times. And if — if he pulled this job — by God, I’ll land him in the hot seat.”

Burks’s eyes had an eaglelike fierceness as he stared down at the face of the dead Government operative. The distorted features and grotesquely mocking tongue of Scanlon seemed to speak of hideous things.

The medical examiner was still going over the body. He shook his head slowly.

“No doubt about it — it’s strangulation. You’d think a slipknot had been tied around his throat, or fingers held there — except that there are no marks.”

“Except!” Burks echoed the word bitterly. The ice-coated branches that were like bony fingers above his head scraped together in a sound reminiscent of soft, sardonic laughter.

Then a detective spoke, touching Burks’s arm.

“Who’s that guy over there?” he asked.

He was looking up the block at a figure that had suddenly appeared. A man swung into sight. He was tall, an overcoat flapped around his heels, and he was coming toward them across the street. Blunt features showed under a slouch hat. He was dressed like a young business man; but his eyes burned with a strange, vivid intentness. He walked up to the group of detectives around Scanlon until one of them stepped forward and barred his way.

“Keep back, guy! There’s been a murder. Who are you?”

The newcomer didn’t answer. He pulled a wallet from his pocket, fumbled in it and drew out a tattered press card.

“A news hound!” said Burks sourly. “How did you get wind of this so quick?”

The stranger uttered one word then, talking with clipped emphasis as though speech were precious.

“Radio,” he said.

“It’s tough,” snarled Burks, “when every Tom, Dick, and Harry listens in on police calls. Headquarters will have to use code for everything if they want to keep the riffraff away.”

THE man with the press card ignored this harsh comment. He pushed closer to the dead man until another detective barked at him to keep back.

When he glimpsed Scanlon’s face, he gave an abrupt, horrified start. The hot flame of some deep emotion sprang into his eyes. His hands clenched at his sides. He breathed quickly, deeply. Then, as if afraid he might be betraying himself, he set his face muscles into masklike inscrutability.

He stood silently staring down at the features of Scanlon, but the strange, burning light in his eyes did not abate. Then he asked a few pointed questions which the detectives answered sullenly.

“If you print any phony story about this, I’ll have your hide,” said Burks harshly. “This is murder — the fourth one like it. Something big is up, see? You’d better be damn careful what you hand out in that lousy sheet of yours.”

The man with the press card nodded somberly. He took another long look at Scanlon’s face as though that face, even with the distortions that hideous death had wrought, were hauntingly familiar. His gaze wandered over Scanlon’s twisted, crumpled body.

Then he lighted a cigarette, puffed on it a moment, and, as if by accident, let it drop from his fingers. But, as he stooped to recover it, his eyes rested for an instant on Scanlon’s exposed cuff, where faint markings showed, unobserved as yet by the police. The slain D.C.I. man had written them there with a pencil, jotted down an address. And the stranger, in the flash of a second memorized that address, storing it away in his mind. Then, as quietly and mysteriously as he had come, he moved off into the darkness.

Inspector Burks, occupied with the murder investigation, didn’t notice the stranger’s absence for a few seconds. When he did, he shot an abrupt, uneasy question.

“Where did that bird go?”

The detective-sergeant at his side looked around in puzzlement.

“I don’t know, chief. I thought he was still here.”

Burks stood scowling, hands thrust deep in pockets, eyebrows drawn together.

“I wonder—” he said slowly. Then he whirled on the men around him and gave a harsh, quick order. “Don’t let him get away. I want to talk to him.”

Two cops broke swiftly from the group, spreading out in different directions, searching the street, their flash lights in their hands. They covered the whole block, then came back shrugging apologetically.

“He beat it, chief. We looked. We couldn’t find him any place.”

There was no one in sight along the dark street; but a sound suddenly rose above the clicking of the ice-coated branches. It was a whistle — faint, melodious, eerie. It had a strangely ventriloquistic quality that seemed to fill the whole air at once.

As Burks stood listening tensely, trying to locate it, it died away. Then, somewhere down the street, an auto engine roared startlingly into life. Gears muttered, whined, grew silent as a fast car swept away into the night.

Chapter II

THE man who had displayed the press card didn’t go to any newspaper office. He drove swiftly through the winter darkness, staring straight ahead. His eyes were like living coals. His knuckles on the black wheel of the car were white and tense.

Before his gaze, the dead, distorted face of Bill Scanlon seemed to hover. Scanlon whom he had known and worked with in days gone by! Scanlon who had guided him, aided him along the rough road of a perilous profession! Scanlon, loyal to the point of death, who had once even saved his life.

What would Scanlon’s wife and young son say when they heard he had been slain? They knew his work was dangerous. They were never sure when he would return. But that wouldn’t make their sorrow at his passing any less.

The man at the car’s wheel muttered huskily, softly to himself. The words came almost like a chant.

“There’s a kid and a woman waiting!” he said.

The glowing light in his eyes seemed to deepen as his lips moved. It grew more steely, more bright, like flame reflected from the polished, gleaming point of a sword. If wise old Bill Scanlon had failed in his mission, fallen a victim to the unseen strangler, then the police must be right. Then this was no ordinary murder menace. The killer back of it all must have the cunning brain of a fiend.

The man of mystery made sure no one was following him. He turned the battleship nose of his roadster into a cross-town street, sped westward toward the river, entering upon a long, smooth drive that followed the curving line of the shore.

Millionaires’ homes and huge apartment houses rose on one side of the drive. On the other were paths and a parkway leading down to the water, curtained now in darkness. The man threaded his way through evening traffic, parking at last on a side street.

He leaped out of the car and walked forward, the burning look of intense emotion still in his eyes. He turned a corner, moved faster still, then stopped suddenly to press a hand to his side. A twinge of pain had come for an instant. Under his fingers was the scar of an old wound received on a battlefield in France.

A fleeting, bitter smile played over the tall man’s lips. Years ago doctors had predicted that the wound would kill him — that he had only a few months to live. But he had gone on living just the same. There was in his body energy that seemed inexhaustible — energy that even death could not seem to conquer. There was an iron will like a living dynamo that drove him on night and day. He had work to do, strange, secret tasks to perform. He wasn’t ready yet to answer the call of the Grim Reaper.

He turned into an avenue running parallel with the drive, walking blocks beyond the spot where he had parked his car before heading back toward the river again. He was on a dark street now — a street deserted, with a high wall on one side of it.

Over the wall, against the night sky, the chimneys and peaked roof of a house were faintly visible. It was a huge pile of masonry, bleak and austere — the old Montgomery mansion left empty by the litigation of heirs who could reach no agreement in the settlement of an estate. It had stood empty for years while the legatees battled like wolves.

The man moved along the wall, creeping deeper into the shadows. Suddenly he stopped. His burning eyes scanned the block in both directions. No one was in sight.

Deftly he inserted a key in a door so nearly the color of the wall itself that it seemed hidden.

The door opened, the man moved inside as silently as a shadow. He was in a place of desolation and ruin now. In the old garden behind the Montgomery mansion.

Statues fallen from their pedestals lay like pale ghosts on the weed-grown grass. A summer house, tumbled down and rotting, showed like the skeletal ribs of a great beast.

He picked his way past a fountain that had long since run dry, entering a rear door of the old house. He moved by feeling alone, moved as one familiar with his strange surroundings.

It wasn’t until he was safe inside the house that he flashed on a small light. He was behind the old butler’s pantry now. Ahead of him were great silent rooms where moths burrowed in the once rich carpets and where rats scurried across the floors.

He pulled at a tier of shelves against the pantry wall, and suddenly the shelves swung outward. The man stepped behind them into the darkness of a hidden chamber. He swung the shelves after him, touched a switch, and lights in the strange room came on. It was a hideout containing many peculiar and remarkable objects.

SEATING himself before a three-sided mirror with movable rod lights above it, the man’s long hands began to do strange, mysterious things to his face. Under their magic touch his whole appearance underwent a transformation.

The blunt, roundish features of the business man melted away, disappeared. The eyebrows changed. The hair of the head revealed itself as an elaborate toupee.

Suddenly the man appeared as he really was — as no one, not even his few closest intimates ever saw him.

The rod lights overhead sprayed radiance on brown hair, on smooth-shaven features that had a boyish cast to them. On gray eyes with a steely glint in their depths.

It was only when he turned to pick something off the shelf that light fell on his face at another angle. Then new lines were brought out — lines that made him seem suddenly older — lines of poise and maturity — with the record of countless experiences and adventures written into them.

He stared at his own reflection for a moment, seeming to salute it grimly.

Secret Agent “X”—the man of a thousand faces — a thousand disguises — a thousand surprises.

The man who was a scourge to the criminals prowling the black alleys of the underworld. The man regarded by the police as criminal himself — even now suspected of murder.

He couldn’t set them right, either. He was committed to secrecy and silence; committed to move into terrible dangers and walk into the shadow of the Valley of Death alone.

The police couldn’t know what document reposed in the strong box on a shelf above his head. For an outsider to plumb its secrets would have meant death. The lid of the strong box concealed a charge of terrible explosive to protect its contents from meddlers. But every word of the document was emblazoned in the Secret Agent’s mind. He could have quoted it from memory, word for word, paragraph for paragraph.

It was unsigned, but it bore the coat of arms of the United States Government. And he knew that the telegram which had reached him that day by way of the First National Bank had also come straight from Washington, D.C. Before destroying the latter, the Agent read it again, committing it to memory as he had the document.

This, too, was unsigned; but was couched in a Government code. The Agent alone knew its high source. Between the lines of it he seemed to read a second, more sinister message, written by the trailing claws of crime — claws that were weaving a horrible spider’s web of murder — building a menace so great that no man could say what hydra-headed horror might rise from it.

Mark Roemer kidnapped! His woman assistant murdered! A taxi driver and an underworld character slain — their bodies left like carrion in a vacant lot! And now brave-hearted, shrewd old Bill Scanlon murdered, too! A sinister crime pattern ran through it all.

Agent “X” crumpled the telegram viciously, touched a match to it, dropped it into a metal dish to burn. Even before he had received it, he had been watching the Roemer case, scenting the unseen miasma of horror surrounding it.

The telegram did not state what formula Roemer had been at work upon, what strange thing he had discovered. But Agent “X” had an inkling. If he were right, then the four ghastly murders were forerunners of others even more terrible.

He faced the mirror again, looked at himself.

Secret Agent “X.” Who was he? No one knew. Whispers there were — whispers in a few high places. There were those who said he had the Government’s backing, that he was a lone campaigner in the war being waged on organized crime.

His fingers began to move again. From a shelf cluttered with jars and sticks of grease paint, nose and cheek plates, and dozens of ingenious makeup devices, he selected what he wanted.

He dabbed pigments on his face, covered his skin with a strange volatile substance and sculptured it into new lines. Strips of transparent, tissue-thin adhesive tape changed the contours of his face muscles. He covered his own brown hair with a white, cunningly made toupee, blackened and thickened his eyebrows. As he worked, deftly, surely, his keen eyes studied a photograph on the shelf before him.

Tonight, in his efforts to unravel the mystery and horror of the strangler murders, he was prepared to take a daring, desperate step.

When at last he rose from his seat, he had the exact likeness of the man in the photograph — a distinguished public official. There was the same silvery-white hair. The same gaunt, thin-lipped face. The same shaggy, menacing eyebrows. Once again “X’s” skilled fingers had achieved a seemingly magical disguise.

He changed his suit and overcoat, dressed carefully, slipped a set of mysterious chromium tools into his pocket, and selected two weapons from his strange arsenal. Then he set out, pausing only long enough to start the mechanism of a hidden seismographic machine which would record the vibrations of footsteps if any one entered his hideout during his absence.

He threaded his way through the desolate garden and out onto the dark street.

Turning his face downtown, he strode swiftly along and hailed a passing cab, being careful to keep his coat collar up and his hat brim pulled down. The light in his eyes showed like a steady, glowing flame. He had started on a vengeance quest for the murderer of Bill Scanlon.

Chapter III

THERE was grim method in the movements of Secret Agent “X” after he left his hideout. Step by step, he began to trace the course of the murder wave that had resulted in his old friend’s death.

He went first to a sequestered suburb on the outskirts of the city. Here he dismissed his cab and walked again through the night. He had followed the strangler homicides in the papers as he did all murder cases that threatened to be difficult of solution. He knew what festering spot had first given birth to the cancer of this hideous crime.

He strode swiftly along a street of badly cared for wooden houses, turned a corner, and came to a lot which at first glance appeared to be vacant. But there was a high barbed-wire fence around it. In its center, dimly seen, was a cluster of low, shabby buildings. They were buildings which were huddled together as though drawing away from the scrutiny of prying eyes. They were dark and silent now. Murder had laid its pall of quietude upon them.

Agent “X” had seen pictures of these buildings in the papers. From this place Mark Roemer, the Government chemist, had been kidnapped. Somewhere among those buildings Roemer’s woman assistant, Cora Stenstrom, had met death at the hands of the invisible strangler.

There was a barbed-wire gate at one side of the enclosure for coal and supply trucks to enter. There was another smaller gate secured by a heavy lock where Roemer and those who came to see him had been in the habit of going in and out.

The Agent paused beside this. A policeman patrolling his night beat sounded measured footsteps up the block. The Agent waited in the light of a street lamp till the cop came alongside.

The policeman stared at the Agent, gave a sudden start, then touched his cap respectfully.

“Good evening, inspector,” he said. “Can I be of any help, sir?”

Agent “X’s” daring disguise had proven adequate. He shook his head, and, when the cop had gone on, he took the kit of chromium tools from his pocket. There were many of them, seemingly fragile, yet cunningly shaped. He held one in his hand, a glittering piece of goosenecked steel. With quiet efficiency he attacked the lock on the gate. In less than a minute the lock snapped open and Agent “X” passed inside.

He moved like a shadow across the barbed wire enclosure toward the jumbled buildings that loomed ahead. He drew another tool from his pocket kit, approached the door of the largest of the buildings. His hand moved toward the lock, then paused. He was staring at the door’s edge.

Someone had been at work here recently. He squinted, nodded understandingly. A burglar alarm had been installed since the murder had taken place. This building was Government property. The work of Mark Roemer had been subsidized by the Government. The Government had taken pains to checkmate any further attempt to pry into the secrets that the building held.

Agent “X” reached into his kit again, drew out a slender band of coiled metal that was like a steel measuring tape. He unwound it from its cylindrical case, probed with the end of it around the door’s edge till he found the plates of the burglar alarm.

Forcing the end of the thin steel under the inside plate, he drew the steel to its full length and thrust the other end into the moist ground.

The Agent knew the workings of burglar alarm systems — knew that there were two plates, and that it was the separation of these two plates when the door was opened that caused the alarm to sound. By grounding the inner plate he had prevented the breaking of the electric circuit.

He now opened the door quietly and entered. Once inside, he clicked on a flashlight with a bulb no larger than a kernel of wheat. It threw a tiny spot of radiance through a concentrating lens, a beam that would not be seen from outside but which enabled the Agent to pick his way. His eyes were glowing eagerly.

He located the laboratory in the building. Here were storage tanks for chemicals and jars and bottles of strange, poisonous-looking acids. Here were gleaming, copper-sheathed retorts, crystal refiners, an air-compressing machine, vacuum pumps, and a refrigeration plant. Here was all the paraphernalia for research into little-known and sinister fields of science. Here was where Mark Roemer and his assistant had worked.

It was from this laboratory that Roemer had been kidnapped. It was in it that the body of his assistant had been found. There seemed to be the dullness of death in this deserted building mingled with the acrid odor of chemicals.

Agent “X” walked to the laboratory’s window, the one that newspaper accounts of the crime said had been jimmied. For long seconds he studied it, raising it softly, examining the marks that the intruder’s jimmy had made. Then he gave a low exclamation.

Marks in the wood of the window frame showed that the pressure which had caused them had come from inside the building. They had been made after the window had been opened. Someone had left those marks purposely, made it seem that the window had been jimmied. The police had apparently overlooked this.

Like a flitting wraith, the Secret Agent moved about the big laboratory, studying, sniffing, nodding to himself. A wide field of chemical research had been under way here. It was impossible to say without careful study what angle of it Roemer had been concentrating upon before his disappearance; but the Agent had his own ideas.

FEELING that he had learned all he could, he left; reconnecting the burglar alarm again, leaving the building as he had found it. He made his way down the street toward a brightly lighted avenue, passing the bulky form of the patroling cop placidly walking his beat.

The Agent’s next stopping point was a vacant lot a half-mile farther on. It was a dreary spot, filled with rubbish and the rusty bodies of old motor cars. A lean cat whisked from behind a barrel looking back at him with lambent green eyes.

The Agent moved between tin cans and piles of rubbish, pausing at last to stare at a bare spot on the ground.

News photographers a few days before had taken pictures of this spot. The tabloids had published the pictures. A thrill-hungry public had gazed at them. It was a spot of death — the spot where a taxi man and a petty criminal, a lone jackal of the underworld, had been found dead. The bodies were gone now; but Agent “X,” reconstructing the crime bit by bit, seemed to see their empurpled faces and outthrust tongues at his feet. They, too, had been killed by the unseen hands of the ghostly strangler.

He looked back at the curb, at the place where the deserted taxi had been found. Then, pondering silently, tensely, he walked on and engaged another cab.

This time he went back toward the city limits.

When he reached the street where the murder of Scanlon had occurred, he ordered the driver to proceed slowly. The Federal detective’s body had been removed. The police cruiser and headquarters car were no longer standing at the curb. But, up the block in front of the address written on Scanlon’s cuff, an official car of some sort was parked.

Agent “X” told his cabman to drive on and turn a corner. He paid his fare, got out, and walked cautiously back.

The house that corresponded to the number on Scanlon’s cuff was a simple two-story affair. There was a light burning on the ground floor. A hedge ran around the yard.

The Agent walked by the chauffeur who dozed at the wheel of the parked car and slipped quietly into the yard. He moved like a shadow along the building’s side. His heart was beating faster now. He was running a great risk. Who was inside?

The shades were closely drawn. He couldn’t see. He would have to trust entirely to his disguise. But before revealing himself he wanted, if possible, to learn what was going on.

He slipped quickly to the rear of the house, tried a door. It was locked, but once again he took his tool kit from his pocket and deftly picked the lock. Then, so quietly that those inside heard nothing, he entered.

He tiptoed to the closed sitting-room door and listened for a moment. A man and a woman inside were talking. The man had the bullying voice of a routine police officer. The tones of that voice were strangely familiar.

“She must have told you,” the man was saying. “We found it on her. She must have known what it meant.”

“No — no,” the woman replied. “She didn’t tell me anything. After Cora went to work for Mr. Roemer I never saw much of her. She was secretive always. I never questioned her.”

“It’s the only clue,” the man’s voice continued stubbornly. “If you can tell me what it means, you’ll be helping the police. You’ll be helping to run down the murderer who killed your sister. Did she ever own a car?”

“No — she didn’t drive, I tell you. She never had a car.”

“You’re sure of that?”

“Yes — yes, I’m sure.”

There was silence for a moment, and in this silence Agent “X” quietly opened the door. His eyes were gleaming. His body was tense. The action he planned was high-handed, unusual even for him; but impulse had its place in his working methods. Here was an opportunity! The police had one clue — one he hadn’t heard of. What was it? The police might not like it — but, to aid in running down the murderer of Scanlon, he would demand that they share that clue with him.

But, as he opened the door, he paused in sudden, breathless amazement. Fate had played a trick on him. The one man he didn’t want to meet was here! Any ordinary dick from the Homicide Squad he could have handled without exciting suspicion. But the man standing in the kitchen facing him was Inspector John Burks, head of the bureau — and his own double!

Chapter IV

IN that first instant it was evident that the inspector had seen him. Utter stupefaction made Burks’s face sag for a moment. His eyes bulged. His thin-lipped mouth opened. So exact was the impersonation that the door might have been a mirror and Agent “X” merely the reflection of himself.

The woman, Cora Stenstrom’s sister, was dumfounded, too. Her gaunt homely face assumed an expression of blank amazement.

In the flash of a second, Agent “X’s” eyes dropped from the inspector’s face to his hand. Burks was holding a slip of paper between tense fingers. On it were letters and figures. Here was the clue that the police had found.

The damage was done now. There was no drawing back. The Agent acted quickly, daringly.

So swiftly that the inspector and the woman could only gape, he crossed the room, gliding up to Burks’s side. He uttered an impersonal, coldly clipped sentence.

“Let me see what you have there, Inspector.”

It was not a request, but an order. Burks’s mouth closed with a snap. His pale, gaunt face flushed to a mottled, furious red.

“Secret Agent ‘X,’” he gasped. There was, he knew, only one man in the world who would attempt such a thing or dare such a disguise. His fingers dropped the paper. His hand dived toward his coat pocket The significant bulge there showed that a police automatic was cradled inside the cloth.

But, in that split second, Agent “X” made his decision. Burks would shoot him dead without question, thinking he had killed a notorious criminal. “X” didn’t give the inspector a chance to draw his gun.

His fist lashed outward and upward in a flashingly swift arc. A hundred and sixty-five pounds of bone and muscle were behind the fist. The Agent’s knuckles struck the point of Burks’s chin. It was a boxer’s blow, straight to the “button.” Without so much as a groan, Burks staggered backward and collapsed. He lay peacefully on the floor, like a man in a deep sleep.

Secret Agent “X” stooped and picked up the paper on the floor. It was only a slip. At first glance the numbers and letters on it seemed simple enough.

“A Green Ford 1920 D EHEC.”

While the woman stood frozen, too terrified to speak, Agent “X’s” eyes ran over it. He realized instantly that it was some sort of cipher. Burks had questioned the woman about it. She had given him no satisfaction. She evidently knew nothing about her sister’s private life. It seemed useless to question her further.

The woman, recovering a little, opened her mouth to scream, but Agent “X” silenced her with an abrupt, commanding gesture.

“Quiet!” he ordered.

With no other word to the amazed woman, he turned on his heel and left the house, striding swiftly through the front door. He walked boldly down the walk and stepped into Burks’s car at the curb. Instead of getting in back, he took a seat directly beside the driver.

“Get going!” he said.

The driver, half asleep, snapped into alertness.

“Yes, sir. Where to?”

Agent “X” didn’t answer. He was holding the slip of paper under the instrument-board light. His face, the face of Inspector Burks, was a blank, but his pulses were racing with excitement. What was this clue that had baffled the police?

“A Green Ford 1920 D EHEC.”

While the chauffeur slid the car into gear and shot away from the curb, Agent “X” studied it.

Those letters at the end of the sentence corresponded to no auto license number he had ever seen. The woman had told Burks that her murdered sister had not even known how to drive a car. Here was mystery. Here was a challenge to the Agent’s cunning. Here also was something that might lead him to the door of the murderer of Scanlon.

“A Green Ford 1920 D EHEC.”

The clue was now in the hands of no ordinary police official. It was in the hands of a man of brilliant insight, a man trained to look beneath the surface and thread his way through the devious, complex channels of cryptography, code systems, and ciphergrams.

He began in his mind to place letters and figures beneath the sentence. He didn’t need any pencil. He had the power of visualization. Seconds passed — and, under the keenness of his analytical brain, the words that had seemed so baffling became understandable.

“Where to, chief?” repeated the driver uneasily. But Agent “X” waved his hand impatiently.

“Anywhere,” he said.

As the car rolled on, a perplexed chauffeur at the wheel, the Agent translated the sentence to his own satisfaction.

THERE were five letters at the end of it — EHEC, preceded by a D. The numbers 1920 puzzled him a moment, then made his task easier. There was no letter in the alphabet corresponding to nought. The Agent therefore took 19 and 20, counted along the alphabet and substituted letters for them — the letters “S” and “T.” Next he substituted numbers for the letters. This gave him 4, corresponding: to D, and 5853, corresponding to EHEC.

To him it was child’s play. The thing was a simple substitution cipher. He now had a telephone number — Stuyvesant 4 5853. He guessed at once why such a simple cipher had been used. The maker of it had counted on the words “A Green Ford 1920” to confuse and throw any investigator off the track. They had so far; but the Agent combined the first words into a name, “A. Greenford.”

His eyes were snapping with excitement. Why had Cora Stenstrom, the murdered woman, carried this name and telephone with her? He remembered the laboratory window with its marks of a jimmy meant to deceive. Had Cora Stenstrom herself opened that window? Her dead lips could never tell, but Agent “X” hoped to fathom their secret.

For a moment he fingered the slip of paper tensely, forgetful of where he was. Then he felt Burks’s chauffeur’s eyes upon him. The man’s face was troubled, uneasy.

“You must ’a found out something, chief. That woman must ’a give you a tip. Where’d you like to go next — if it ain’t too much trouble?”

“That’s a good question,” said Agent “X” grimly. “I’m looking for a murderer.”

“Yeah, I know it, chief, bu—”

“A kid and a woman are waiting,” muttered “X” again softly, thinking of Bill Scanlon’s wife and young son, seeming to see once more the face of a man who would not come back. A sudden harsh look sprang into his eyes.

The chauffeur lifted a hand from the wheel and, in spite of the winter chill, wiped sweat from his forehead. His face was twisted nervously now. He seemed to sense that something was wrong. There was a look of fear and awe in his eyes as he glanced sidewise at his superior.

Secret Agent “X” laughed shortly, bitterly. They were crossing a brightly lighted avenue. Another dark street was ahead.

“Just keep going,” he said, “I’ll tell you when—”

He stopped speaking. Another sound had cut in upon his words. The short-wave police radio in the front of the car had suddenly come to life. There was a rattle, a buzz. The chauffeur touched the dial.

“Calling all cars!” came the voice of the headquarters’ announcer. “Calling all cars. Look out for—”

With a movement so quick that the eyes of the chauffeur could hardly follow it, Secret Agent “X” reached out and turned the dial, cutting off the voice.

“Stop right here,” he said quickly.

The car came to a halt with a screech of brakes. Agent “X” jumped put, then paused for an instant, staring back at the wondering eyes of the police chauffeur.

“What is it, chief? What’s the matter?” the man asked.

With a strange, sardonic smile on his lips Secret Agent “X” reached into his pocket He drew out the slip of paper with the code upon it, handed it to the chauffeur.

“Give that to Inspector Burks,” he said, “with my compliments.”

“Inspector Burks! Why — what the hell!”

Words tumbled from the chauffeur’s lips; but Secret Agent “X” didn’t wait to reply. He slipped around the car, darted across the sidewalk into the shadow of a hedge. The darkness seemed to open up, swallow him.

But behind him, as the excited hand of the chauffeur turned it on again, came the blatant, metallic sound of the police radio.

“Look out for Inspector Burks’s official car driven by man impersonating him. Chauffeur believed murdered. Look out for escaping killer. Calling all cars!”

WITH the gleam of sardonic amusement still in his eyes, the Secret Agent ducked between two houses, crossed to another street, and continued on into the night.

He stopped for a moment in the blackness of an alley to change his disguise. As the impersonator of Inspector Burks, he was a marked man now. Police cars would be combing the city. His present make-up would be like a death warrant.

His quick, deft fingers removed it, and pulled other materials from a deep inner lining of his coat. Disguises that took patient minutes to build up could be destroyed quickly. He had other stock make-ups for just such emergencies as this.

Working in the dark by a sense of touch alone, he drew the white toupee from his head, changed it to a gray one, and molded his face into new lines.

He came out of the alley disguised as a man of middle age, with thick lips and sagging face muscles. Then he walked through the night-shrouded streets to the nearest drug store. In a telephone booth, he dialed information. He gave the number he had deciphered and learned that it was the Hotel Sherwood.

Step by step he was creeping ahead. Creeping toward what? Toward the solution of the mystery, toward defeat — death? It was certain that the person who had committed four terrible murders wouldn’t stop at committing others. It was certain that menace like a sinister shadow darkened the path that “X” had chosen to follow.

Still disguised as a well-dressed man of middle age, he took a taxi to within two blocks of the Hotel Sherwood. Smoking a cigarette, he walked into the lobby. It was one of the city’s smaller, less expensive hostelries. A place where many transient out-of-towners stopped. His presence attracted little attention. And “X” always prepared for small emergencies, acted deftly, swiftly, now.

He fished in his pocket, drew out a complimentary theater ticket that had been handed to him in a restaurant. Dropping this into a yellow envelope, he sealed it and wrote “A. Greenford” on the outside. He moved across the lobby, dropped the envelope on the reception clerk’s desk, and, even before the clerk had seen it he went back to a seat beside an ornamental palm. From here he saw the clerk pick up the envelope and place it in a numbered box.

A half hour went by, an hour, while the Agent waited tensely. Many cigarettes passed through his fingers. His nerves were screaming for action. Then, from the corner of his eye, he saw a dark, quick-moving man come out of the hotel’s elevator.

The man walked jerkily to the desk and asked a question. The clerk reached into the tier of boxes behind him, drew out the yellow envelope and tossed it on the counter. The Agent’s eyes, brightly alert, took in every move.

The dark man opened the envelope, frowned at the ticket and threw it irritably into a cuspidor.

Still frowning, he turned and moved toward a seat in the lobby. He had a brownish, pasty complexion, thin, cruel lips and deep-set eyes.

He stopped suddenly, turning his head toward the door.

Newsboys in the street outside were crying shrilly, shouting:

“Extra! Extra!”

One of them came into the hotel’s lobby brandishing a paper.

“Extra! Read all about the big murder! Federal man killed! Read all about the big murder!”

The dark-faced Mr. Greenford jumped out of his chair and stepped forward tensely. He fumbled in his pocket, produced coins, and bought a paper. Agent “X” watching intently, noticed the sudden change that came over Greenford’s face. Its pastiness seemed to increase. Evil lines showed around his thin mouth. He retired to a corner with the paper in his hand.

Agent “X” quickly signaled the boy and bought one himself.

Here was the terrible story of Bill Scanlon’s murder. Here was a picture of him and his wife and small son. Here was the record of his long and faithful service with the Department of Criminal Investigation. Telegraph wires had been humming. The tabloid presses had been busy spewing out a special edition to broadcast this latest strangler horror. The police had been forced to release details to eager reporters. The papers had played it up.

“Unseen Strangler Claims Fourth Victim,” the headlines screamed.

But Agent “X” hardly glanced at the story inside. He knew more than these startling lines told. He was watching the man who called himself “A. Greenford.”

The dark-faced stranger was devouring the details of the killing, his long, thin hands trembling, one black eyebrow twitching nervously.

MINUTES passed. The man did not move. Then a uniformed telegraph messenger stepped into the hotel lobby. He went to the desk, handed a telegram to the clerk. The clerk signed for it, gave it to a bellhop. The bellhop’s voice rose.

“Paging Mr. Greenford. Telegram for Mr. Greenford.”

Agent “X” acted swiftly, daringly again. He rose from his seat, held his hand up and signaled to the boy. Before the angry, incredulous eyes of the dark-faced man in the corner, he snatched the telegram and slipped a shiny quarter into the bellhop’s hand. Then abruptly, he slit the envelope with his finger and read the message inside.

“Arthur Greenford, Hotel Sherwood,” it said. “Come to No. 40 Bradley Square, top floor, rear, midnight. Important. B.M.”

The Agent saw that the dark-faced man had leaped out of his chair and was coming toward him. He did not wait. Thrusting the telegram into his pocket, he turned and walked swiftly to the door.

He knew that he was being followed. There was an excited gleam in his eyes. The message of the telegram carried mystery with it. It was almost as mysterious as the sentence found on the body of the murdered Cora Stenstrom — the sentence that Secret Agent “X” had deciphered. Who was B.M.? What motive was behind his midnight invitation? Agent “X” would find out.

Theater crowds were thick on the sidewalk outside. Laughing, jostling people moved along beneath the bright, gay lights. They stared at the gaudy, alluring theater posters, blinked at the flashing neon tubes. They did not sense, as “X” did, the sinister spirit of murder that seemed to stalk through the night.

He mingled in the crowd quickly, but not too quickly. He turned his head once. The dark-faced man behind him was catching up. Agent “X” lighted a cigarette. He strode ahead as though preoccupied with his own thoughts. He did not turn when someone touched his arm. Then a hoarse voice spoke in his ear.

“Wait — you have something of mine!”

Agent “X” looked around then. The man who called himself Arthur Greenford was standing tensely at his side. His face was contorted with emotion. Fear and suspicion glared from the depths of his black eyes.

“That telegram was meant for me,” he hissed. “What did you mean by taking it? Who are you?”

Agent “X” faced him squarely. His own eyes were blazing with excitement.

“Perhaps my name is Greenford, too,” he said.

“Perhaps — and perhaps not. You will give me that telegram, or—”

There was a sinister threat in the man’s incompleted sentence. The Agent smiled bleakly.

“You shall have it if you want it,” he said. “A most unfortunate mistake!”

His hand dived into his packet. It came out clutching the yellow telegram. Greenford could not see the small metal tube concealed in the palm of the Agent’s hand. The jostling crowd milled around them. Agent “X” held the telegram out. Greenford reached out a hand to take it. The Secret Agent’s fingers moved. He held the tube tensely, skillfully. His thumb was pressing one end. From the other, the open end of the tube, a hair-thin needle flashed out. It penetrated the skin of Greenford’s wrist, buried itself for an instant in his flesh. The prick of its point was hardly more noticeable than the bite of a mosquito.

Greenford drew his arm away, hardly knowing what had happened. He glanced at the Agent, glanced around. But the telegram was in his fingers. Its message seemed to hold him fascinated. He had not seen ths Agent palm the tube, a miniature hypodermic needle. An instant more and Secret Agent “X” had turned his back and was striding on.

Greenford called after him, started in pursuit again. But he had taken no more than a half-dozen steps when he began to stagger. He fell against a woman at his left, pulled himself up, and swayed to the right. Then suddenly his knees gave way under him. With his face muscles sagging and a look of utter perplexity in his eyes, he fell to the pavement.

Excited shouts went up from the crowd around him. Greenford was sitting on the sidewalk with a dazed look on his face. He was like a man afflicted with a sudden apoplectic stroke. The crowd stopped, drew around him in a ring, staring with dumb, gaping eyes.

“He’s drunk,” someone said.

“He’s sick,” said another. No one made a move to do anything about it. A lethargy of curiosity had settled over the people around — the lethargy of the typical city crowd.

Then a man broke through the barrier of gaping people. His face was concerned. He was a dignified-looking man, gray at the temples, heavy featured. He had a professional air about him. The man was Agent “X” come back.

He felt Greenford’s pulse — rolled his eyelid down and stared at the iris.

“I’m a physician,” he said. “Call a cab — at once. This man seems to be ill.”

Someone at the edge of the crowd signaled a taxi. The cab drew up to the curb. Someone else helped Agent “X” lift Greenford to his feet. In a minute he was inside the vehicle. Then, with Agent “X” holding him solicitously, the cab sped away.

Chapter V

“TO the nearest hospital,” ordered Agent “X,” still maintaining his professional manner. The driver nodded, heading the cab into a long avenue, honking his horn to keep traffic back.

In the interior of the cab, slumped on the seat, Greenford’s body joggled like a sack of meal. His head swayed grotesquely on his shoulder. His dazed eyes stared ahead unseeingly.

But as seconds passed, the vagueness of his eyes began to diminish. It was as though a curtain were slowly going up. Agent “X” opened a side window. Cold night air blew on Greenford’s face. A little of the laxity left his body. He shook himself, opened his eyes wider. A sound like a sigh came from his lips. Suddenly he moved his head, stared at the man beside him. His gaze met the strangely burning eyes of Agent “X.” A snarl came from Greenford’s lips, then color rushed back into his cheeks, mottling them darkly.

“Who are you?” he demanded.

Agent “X” did not answer immediately. He reached forward with one hand, slid the glass panel behind the driver’s seat shut.

“Silence!” he said harshly.

“See here—” Greenford was crouched back on the seat now like an animal at bay. “Let me out of this cab or I’ll—”

There was thickness in his voice, the thickness of some foreign accent carefully hidden. He yanked his arm away from the Agent’s grasp, his fingers moved suddenly toward his pocket, then hesitated. The burning, strange light in “X’s” eyes seemed to hold his fascinated. “X’s” right hand had moved, drawn his gas gun out so quickly that Greenford had been unable to follow the motion. The gun was pointed directly at him now. He could not know that its sinister black muzzle held only sleep, not death. The look in the Agent’s eyes was deadly.

The Agent offered no explanation, gave no inkling of his plans. But the look of anger in Greenford’s face turned to one of fear. A sickly doughiness came over his features. He began to tremble. There had been murders. Murder was in the air. In the eyes of this strange man beside him he seemed to read a sinister threat.

“Don’t shoot,” he babbled suddenly. “Don’t kill me. I’ll do anything you say.”

Here was the voice of a coward speaking, a man whose aggression left him when he saw himself cornered. There was contempt in the Agent’s eyes. He had met this breed before. He held the gun steadily. Then he slid the panel behind the driver’s seat open, again.

“Never mind the hospital,” he said. “Drive to the St. James apartments — ninety Jefferson Avenue.”

The cabman gave one puzzled glance and obeyed. If he thought at all, he must have concluded that the address given was a doctor’s office.

Greenford continued to tremble, staring with terrified eyes at the man beside him. Agent “X” seemed to radiate mystery and power. There was inexorable command in his glowing eyes. Their glance was almost hypnotic. Greenford wilted beneath it.

The cab drew up at the address given. A big but not too expensive apartment rose at the side of the street.

Agent “X” thrust the gas gun in his pocket, but kept the muzzle still pointing at Greenford through the cloth of his overcoat.

“Make any break and—” “X” did not finish his sentence, but he pressed the hard snout of the gun against Greenford’s side.

The Agent paid the cabby then, and, with Greenford moving slightly ahead, they entered the apartment building. There was no doorman. A switchboard operator glanced at them casually. Agent “X” pressed the button of an automatic elevator. When the car came into sight, he motioned Greenford into it. He pressed another button, and they ascended to the fifth floor.

Greenford, still trembling with fear, was marshaled down a long corridor and into a simply furnished apartment. The door of the apartment closed after him.

“What do you want?” he asked in a croaking voice. “Who are you? I haven’t got—” He did not finish the sentence. He checked himself, stared at the Agent.

The Agent was silent. His burning eyes were still upon Greenford. He seemed to be studying him, seemed to be analyzing every movement that the man made. Greenford spoke again.

“What is it you want. Don’t—”

Again he stopped in the middle of a sentence. His lips opened to scream, but the scream ended in a gasp. For, as quickly as the flash of a snake’s tongue, Agent “X” had whipped his gas gun out. His finger pressed the trigger. There was a barely audible hiss. A jet of gas sprayed into Greenford’s face, filled his mouth. Without a sound, the man staggered back and collapsed on the rug.

THE Agent pocketed his gun; then drew an open-faced watch from his pocket and glanced at it. It was long after ten now. The telegram he had taken from Greenford had given twelve as the hour of the mysterious rendezvous at Bradley Square. Time was a vital element.

He stooped over Greenford, picked him up. Unobtrusive but steel-like muscles in the Agent’s shoulders snapped into life. As easily as though he had been a child, he carried Greenford’s unconscious body to a big chair and deposited it there, placing pillows behind Greenford’s back, propping him.

Then once again he began studying the man’s face. He studied it from all angles, noting the planes of it and the lines.

He walked to a closet in the apartment, drew a suitcase out, and turned it upside down. He pressed two brass studs in the suitcase’s underside and disclosed a cleverly concealed false bottom that would never have been suspected unless the suitcase’s sides and depth were measured. From this secret compartment he took an assemblage of make-up material. Thin vials of pigments and volatile plastic substances.

He locked the apartment door, spread his make-up equipment before a bureau mirror, and set to work. Glancing from time to time at the unconscious man in the chair, his fingers performed the magic that had made the Agent’s name one to conjure with. The man of a thousand faces — a thousand disguises — a thousand surprises, was at work again.

For twenty minutes his fingers moved dexterously. When he turned at last from the mirror, Greenford’s double seemed to be in the room. Agent “X” walked across the floor practicing Greenford’s characteristic movements. The Agent’s disguises went further than make-up. They became a study in muscular coordination as well. He spoke a few sentences, mimicked Greenford’s slightly blurred accent.

He searched Greenford then, took a wallet and papers from his pocket and found a money belt strapped around his middle next to his skin. The Agent’s fingers were tense as he opened this. It was stuffed with bank notes — bills of high denomination. He looked at their corners. A one and two noughts showed. Century notes!

He counted them. Fifty of them — five thousand dollars! Stacking the bills in a neat sheaf, the Agent pocketed them. They were not for himself. He had no need of money with the account in the First National Bank always ready to draw on. He had never made the test, but he felt sure that his own resources were practically unlimited. But he had a strange outlet for money confiscated from criminals.

There were blank papers in Greenford’s wallet. Agent “X” suspected that they held writing in invisible ink. They might give insight into Greenford’s strange vocation. But there wasn’t time to search for a chemical developer now — and the Agent had already drawn his own conclusions regarding Greenford’s character.

He drew the small hypo needle from his pocket again; emptied the colorless liquid from its tubular syringe, and refilled it from a small vial. This he injected into Greenford’s arm, close to a vein. The man would stay unconscious for a specific time now, or until “X” chose to administer an antidote.

Next he put Greenford’s slumped body into a ventilated closet and locked the door.

It was now after eleven. He descended to the street floor and passed the switchboard operator, who took him for a departing guest. He walked several blocks and hailed a cab. What strange and sinister adventure, he wondered, lay ahead of him at No. 40 Bradley Square?

Chapter VI

ONE thing he saw in his first glimpse of the house, and he gave a start of amazement. The building was closed up. It was a four-story brownstone mansion belonging apparently to the Victorian era. Protective boarding covered the windows on the first floor. The others on the floors above were dark and curtainless. There was a “for sale” sign on the building, showing whitely under the glow of the corner light. Bradley Square had become run down. Its past glories were gone. It was a place of quiet and decay. The once-flourishing park in its center had been turned into a playground for poor children. Deserted swings hung forlornly in the darkness like gibbets.

A drunken man moved tipsily toward the garish doors of a beer saloon at the far end of the square. A few rooming houses on the side where number forty stood showed dim lights through dusty windows.

The Agent walked past the house of mystery several times. What mad thing was this to bring a man to a deserted house? The dark, empty windows seemed to frown down upon him. Were there eyes watching him furtively somewhere in the blackness?

He looked at his watch again. Exactly midnight. A clock blocks away boomed the hour, sending cracked echoes across the square. The icy branches of the trees rattled in the night wind, making him think again of Bill Scanlon’s staring eyes and protruding tongue. Death seemed to lurk in the night around him. There was a grimly sardonic gleam in the depths of his eyes. It was into such situations, such places, that his strange commission led him.

He mounted the steps of number forty, pulled the metal end of an ancient bell wire. Somewhere far back in the empty house a thin jingle sounded. He listened. There was no answering sound of footsteps. He pulled the bell wire again. The jangle that awoke faint echoes seemed almost sacrilegious, as though he were disturbing the quiet of a mausoleum — disturbing the dead.

Then the hair on his scalp rose. He held himself tensely. Before him, the weather-worn door of the house opened. There was no one in sight, no sound of a human being, only the faint rusty movement of the hinges. A draft of stale air struck his face. The hallway before him was starkly empty. It was uncanny, awe-inspiring — more so than the sight of any sinister figure. The ghostly movement of the door made him think of the phantom strangler, of the invisible, awful thing that had already snuffed out the lives of four people.

But he moved into the house. It was cold inside with the coldness of a place that has long been empty. Behind him, with an eeriness that made his hair rise, the door swung shut. He was in absolute darkness. Was this a death trap? Had someone planned to lure Greenford to his doom? The Agent smiled bleakly again. He had lived too long in the presence of the Grim Reaper to fear him now. He had cast fear from his heart.

He struck a match, moved forward along the ancient hallway toward a flight of stairs ahead. The paint on the old walls was cracked and blackened with dust. The red plush carpet beneath his feet gave out little puffs of dust as he moved, and ahead, in the doorway leading to the big old-fashioned parlor, tattered, moth-eaten draperies hung, a last relic of decayed and dead gentility.

The parlor was as black as the opening of a tomb. He passed it quickly, ascending the stairs. “Top floor, rear,” the telegram had said. He moved past floor after floor, striking matches. In the wavering brief light that they shed, his shadow seemed to pursue him like a stalking fiend. He did not use his flash light. To do so would be out of character. It might throw suspicion on him if unseen eyes were watching.

He came at last to the top floor. Here all street noises were excluded. There was no sound anywhere in the old house. The house seemed to be silent, crouching, like a beast waiting for its prey.

The door of the rear top room was shut. He opened it, passed inside. The curtainless windows admitted a ghostly glow from the light in the next street far below. He saw a few pieces of broken furniture that the last tenants of the house had left behind. A springless iron bed, a chair with one rocker gone, a metal washstand twisted into a shapeless mass of rusty iron. There was no one in the room — no living thing. There was a closet and he opened the door of it, struck a match, looked in. That too was empty, save for a man’s old overcoat hanging there like a withered corpse.

BUT as he stepped to the center of the room again, a voice suddenly sounded — a voice so close and so harsh that it was like a dash of icy water thrown on him.

He couldn’t locate its direction. It seemed to fill the whole room. It seemed to come from his left; but only blank wall space was there. He listened.

“Greenford,” the voice said. “Greenford,” it repeated again and again. “You are nearly a minute late, Greenford. It is not wise to come late to this house when an appointment has been made. I expect those with whom I have dealings to be on time!”

The voice ceased as abruptly as it had begun. It was a man’s voice, harsh, grating. It was a voice that gave Secret Agent “X” some inkling of the sinister being that he was fighting, a voice that had the assurance and cruel arrogance of supreme power.

Mimicking Greenford’s accent, Secret Agent “X” answered.

“The slippery pavements made haste difficult tonight. I am sorry — so sorry.”

The voice spoke again.

“Some men learn by their mistakes. Others do not. You will learn to be punctual, or—”

A harsh laugh sounded — a laugh as brutal and evil as the scraping of a poisonous reptile’s scales. Then the voice continued:

“I have what you want, Greenford. By murder I gained the thing you sought. Gold would not buy it for you. Death gave it to me. But for gold I will part with it. What amount, Greenford, is your government prepared to pay? Consider well. You have twenty-four hours for cable negotiations. Come tomorrow night at this same time. Take warning! Do not be late! Speak in this room and I will hear. Let me know your answer. I have other customers if your price is not satisfactory. And make no attempt at trickery. You are helpless. You are in the hands of the Black Master.”

The voice ceased again, and silence descended on the room, as heavy as the silence of a tomb. Agent “X” pondered a moment.

B.M. had been the initials on the telegram Greenford had received. B.M. — The Black Master. But who was this criminal who held the city in a thrall of fear? Who was this killer who had brutally murdered four people, among them loyal, brave-hearted Bill Scanlon of the D.C.I.?

The silent room and the old house gave no hint.

The fingers of “X’s” right hand tautened for a moment, clenched till the knuckles went white. His lips moved slightly, whispered again that phrase that seemed to ring through his head.

“A kid and a woman are waiting!”

He had come close to the murderer of Scanlon — heard him speak. Yet it was as though rocky walls separated them. He dared not strike now, dared not search through that room as he wanted to. He must wait, watch, proceed with the caution and cunning of a fox. A false step — and all would be lost. The horror would go. Scanlon’s cruel killing would never be avenged.

He descended the dusty stairs quietly. His eyes held an inscrutable light. He had till tomorrow night to make a decision. But he was still in darkness, darkness as total as that in the black corridor below. The door opened for him again as though the ghost of some ancient, silent servant still lingered in the dim hallway.

He passed out into the street. Night wind struck his face. The ice-coated branches whispered like mocking laughter.

But as he moved along the street, it seemed for an instant that a shadow moved after him. He had trained himself to see such things. He had shadowed men himself and knew the arts of shadowing. He was being shadowed now. Of that he was certain.

For a bare second he paused. His only hope of running the killer to earth lay in seeming for the moment to comply with the voice of the Black Master. He walked on, conscious still of eyes upon him.

He passed beyond the square and came to a thoroughfare. Standing at the curb, he signaled a taxi. His eyes glinted grimly as, looking back, he saw another taxi go to the curb, pick a passenger up and follow.

“The Hotel Sherwood,” said Agent “X.”

Posing as Greenford, he must play the role of Greenford until—. It seemed now that the cunning of his brain was the only power on earth that could sever the terrible murder chain that unseen hands were forging.

His cab drew up before the bright lights of the Sherwood. The other taxi was no longer in sight. Agent “X” paid his fare and went into the lobby. He picked up Greenford’s key at the desk and ascended in the elevator. He was revolving a hundred plans in his mind, wondering what course was best to follow. The man he was battling was a monster — a criminal without scruple, and with infinite cunning. High stakes were at issue. The caution the Black Master had taken proved that. But, even if there were nothing else, the murder of Scanlon was motive enough to drive Agent “X” forward into the very gates of death.

He opened the door of Greenford’s room, closed it after him, groping for a light switch. He clicked it on, and the overhead bulbs bathed the chamber in radiance. Then suddenly the Agent held himself taut, holding his breath and with muscles contracted. A woman’s voice, sinister as the purring of a sleepy tigress, spoke close to his ear.

“Armand — are you not glad to see me?”

Chapter VII

AGENT “X” turned his head slowly, stiffly. For once he had been caught off guard. For once the utterly unexpected had happened.

A woman, blonde and dazzlingly beautiful, stood beside the door. Crimson lips smiled at him. He caught in that first glimpse the feline, arrogant grace that characterized her bearing. She was leaning against the bureau, one hip thrown out, a hand resting on it, the other hand holding an unlighted cigarette. Her close-fitting dark dress revealed the superb outlines of her figure.

Slowly she lighted her cigarette, took a deep puff, blew smoke through her delicate nostrils.

“You are surprised! You did not expect to see me,” she said.

Her lips smiled again; but her eyes did not. They regarded Agent “X” with cold, impersonal calculation. The silvery tones of her voice, her sleekness, her beauty, masked something else — something sinister. Here was a woman as dangerous as she was lovely. A tiger woman who lived by her wits and that stinging provocative appeal of her charms. Who was she? The Agent could only guess. He had pulled himself together. He began playing a game — a deadly, silent battle of wits.

“I am surprised — yes,” he said. “But a beautiful lady is always a welcome surprise.”

She laughed throatily, came nearer. He could smell the faint clinging perfume that seemed to envelop her.

“You used to call me Nina,” she said.

“Nina is a lovely name,” he replied.

He lighted a cigarette himself, stared at her, waiting and watching, his eyes narrowed. A false move and she might grow suspicious. He must not slip out of his role — the role of Arthur Greenford — the man she called Armand.

“It was clever, changing your name,” she said. “But why did you choose the same initials? Arthur Greenford — Armand Grenfort?”

He bowed ironically.

“I did not expect that my initials would undergo analysis by such an astute brain as yours.”

She laughed again, but her eyes that were dark and bright as polished agate took on the hardness of agate.

“You are fencing with me, Armand. Do you think I do not know why you are here?”

Her accent and phrasing were foreign. He had catalogued her already. The theft of Mark Roemer’s mysterious formula had brought another evil vulture circling about. For in spite of her beauty, the woman before him had in her eyes the look of some predatory bird or beast.

“You are just as subtle as you used to be,” he said softly.

She came and laid her hand on his arm, brushing her lithe body against him for a moment. Her lips, smiling up at him, were challengingly close.

“Perhaps,” she said, “we can work together — as we did once before.”

He tried a shot in the dark then. He made his voice harsh.

“It’s too late, my dear Nina. What I seek is gone. It has been stolen. It is in the hands of another.”

The woman pushed him away from her roughly. She stepped back toward the bureau again. A transformation came over her. Hate and greed convulsed her face, making her look suddenly older, bringing out wicked lines in her features.

“You lie!” she said, and the two words came from her lips like drops of distilled venom. The beauty of her body was like the sinuous beauty of a cobra swaying, ready to strike.

“You lie!” she repeated.

He stood looking at her, shrugging.

“Listen,” she said fiercely. “You will let me work with you — share with you, or—”

Her slim hand suddenly reached behind her. She snatched something from the bureau top which she had concealed under a lacy handkerchief. It was an automatic, flat, polished, small as a child’s toy — but capable of dealing death. She pointed the gun at the Agent’s heart, held it tensely as though it would give her pleasure to shoot. He did not doubt that she had killed men before.

Again he shrugged.

“What about the kidnapping of Mark Roemer and the murder of his assistant?” he asked.

Her lips slid back from her teeth in an evil smile. They formed a crimson, mocking gash across the front of her white face. She nodded craftily.

“I know,” she said. “Mark Roemer was kidnapped. His assistant was murdered — not prettily either. I read all about it. That is why I came to see you. You did it, Armand. You are bolder than you used to be. Men learn by their experience. You murdered that woman — and those others. You have Roemer somewhere and you are guarding his secret. If you are not generous with me, Armand, I will turn you over to the police — right now.”

“And if I am — generous?” he asked.

“I will forget what I know about you. What is a murder — between friends?”

THE depth of her wickedness was appalling. It was like finding a deadly, coiled serpent concealed in the soft petals of a flower. She was blackmailing him, ready to wink at murder — if he would satisfy her greed.

He shrugged again, resignedly this time.

“You always had strength of character, Nina. You had a way of getting what you wanted. But I’m tired and there are many things to be gone into. Let us go out and discuss this over a bottle of wine. If we are to work together — we must renew our acquaintance — for old time’s sake.”

She stood glaring at him, doubt in her eyes.

“Any tricks, Armand — and I will anticipate the law. I will kill you!”

“Are you not a little frightened,” he said, “trying to browbeat a murderer?”

For a moment the paleness of her face increased.

“I left a note with certain friends,” she replied. “It is to be opened — if I do not return. In it are facts about you — details to aid the police.”

“In that case,” he said, “we are assured of a quiet evening. I am certain we will get on amicably.”

She nodded and put her automatic into a hand bag.

“We understand each other, Armand,” she said.

The Agent smiled to himself. He understood her, knew that she was an unprincipled spy in the pay of some government, and that she had once worked with Greenford, or Grenfort. But it was ironic to think how utterly in the dark she was concerning the affairs of the real Grenfort. He had spoken the truth and she had not believed him.

She came then and lifted her lips to his, slipping soft arms around his neck.

“We used to be such good friends, Armand!” Her words were a caress and an invitation.

“Let us not mix business with pleasure,” he said coldly.

He saw hatred flash in her eyes again. But she began dabbing powder on her face from a silvered compact. Then she slipped into a clinging fur coat that was thrown over a chair. It made her seem more feline than ever.

They descended in silence to the lobby below and turned their faces toward the street. There was a cab waiting at the curb. Agent “X” ushered her into it and gave the address of a small restaurant.

The woman settled herself beside him.

“Remember,” she said, “there is a note waiting to tell the police — everything — if I should disappear.”

“Let me repeat that I hold your life as precious as my own,” he said mockingly.

She looked at him keenly for a moment.

“You have changed, Armand,” she said. “You have more steel in your character than you used to have. That is what murder does for a man.”

Suddenly he saw her eyes widen, and a hiss came from her lips that was like the hiss of a startled snake. She was looking back, looking out the cab’s rear window. Her fingers tightened over the Agent’s arm like clutching talons.

“Armand,” she said, “we are being followed. Look — there are men in that car — and they are watching us.”

Chapter VIII

AGENT “X” stared back tensely. He was not afraid for his own life. He was afraid only that something might impede his progress in tracking down the Black Master — the invisible strangler. In his first glimpse of the men behind, he catalogued them. There were four, grim-faced, clean-cut. One at the wheel of the car, another beside him, two in the back seat.

One was leaning out, signaling for the cab to stop.

Agent “X” bent forward, jerked the glass panel behind the driver’s seat open and hissed in the driver’s ear.

“Gangsters behind,” he said. “Speed up — for your life!”

With a startled twitch of his head, the driver stared back, saw the pursuing car, stepped on the gas. The taxi leaped ahead like a horse under the lash of a whip.

Agent “X” leaned back smiling grimly. The men behind were not gangsters. They were Department of Justice operatives. Of that he was certain. He knew the type well. But it had been necessary to lie to the cabman to save the situation. Nina, the woman beside him, caught the fleeting smile on his face.

“You — you tipped them off!” she hissed. Her hand flashed toward her hang bag again. He caught her wrist.

“Don’t be a fool. You accuse me of murder. Would a murderer tip off the law? They must have trailed me.”

The woman blanched and began to mutter fiercely. She was no longer beautiful. She was a harsh-faced tigress.

“They must not get us,” she cried. “We will shoot — shoot to kill.” Again she dived for her weapon. Again he stopped her.

“You will do as I say,” he grated. “You came to my hotel. Perhaps it is you they followed!”

“No,” she said fiercely. “I came by plane from Mexico. It was night when I landed. They could not have seen me. It is you, Armand, that they are after.”

“You are a notorious woman,” he answered, again making a stab in the dark. “The American Secret Service has a hundred eyes. Spies are always under suspicion — but they must not catch us.”

“No — no,” she echoed. “I cannot be found with you. I will be deported — perhaps jailed. They will suspect me of being implicated in the murders you have committed.”

“And,” he said mockingly, “you will lose the money that I am supposed to divide with you.”

He leaned forward, spoke to the driver again.

“Faster — they are catching up.”

The man leaning out of the car behind had stopped signaling now. His face under the glow of a street light that flashed past had the grimness of granite. Something gleamed in his hand.

“They are going to shoot!” screamed Nina.

Her sentence was punctuated by the slap of a bullet against the rear of the taxi and a crashing report in the street behind. The cab leaped ahead again as the driver sought frantically for more speed. A second bullet struck the glass in the cab’s rear, splintered it, sent it tinkling between the Agent’s and the woman’s laps. Cold air rushed in. Nina screamed again shrilly. For a moment he thought she was hurt. Then he saw that it was fear. A tiny sliver of glass was sticking in the back of his hand. He pulled it out deftly.

“You don’t care,” she said. “You don’t mind that I may be killed!”

“My dear Nina—” he expostulated. The intense glow in his eyes showed the excitement that steely nerves were keeping under control.

The cab flashed across a street against traffic lights. Brakes squealed madly as another car stopped just in time. A policeman’s whistle shrilled. The cab plunged on.

THE driver’s neck and cheek — all that Agent “X” could see — were white as a sheet. His hands were wrapped stiffly around the wheel. A third bullet whizzed between the two in back, slapped against the glass partition close to the driver’s head. He cried out and the cab lurched and bucked as his arms jerked in fear. It threatened for a moment to go over. Then the driver straightened it out. He pressed the gas button down, put on a final burst of speed. They drew ahead a little. A fourth bullet went wide.

“To the park!” barked the Secret Agent. “Turn left — the first gate.”

Somewhere behind them now a police siren was wailing. But even the green police cruiser could not catch up. The heavy engine of the taxi was pounding under its metal hood. The rubber tires were whining over the pavement. Traffic was at a standstill. White-faced pedestrians scuttled out of their way, or stood staring fearfully on the sidewalk. The papers had been filled with stories of gang warfare. This looked like an example of it.

The cab’s engine began to pound then. It wasn’t built for such high speeds. Somewhere a gasket had blown. The cab was slowing down.

Agent “X” looking back saw that the car behind was gradually drawing nearer. Its headlights were goggling like the eyes of a monster. Two men were leaning out now, their faces purposeful, waiting till they were within small-arm range. They were aiming low, getting ready to shoot for the tires. Blown rubber at such speed might be as disastrous as a bullet. The menace of death rode with them in the night.

The woman, Nina, was white-faced now. Her blonde hair was spilling from beneath her hat. She looked suddenly haggish, witchlike, evil as a mad vulture. Her voice had a harpy shrillness.

“They’ll get us! We can’t escape!”

The Agent made no reply. He saw the park ahead of them. The stone pillars of the gate swept toward them. The taxi hurtled at the gates like a speeding ball headed for two goal posts. It was late. The park was dark and empty. The concrete road ahead was a smooth speedway. But the engine was hissing and pounding at every stroke.

The car behind leaped through the gateway of the park like an avenging nemesis. It roared down upon them out of the night. There was no danger of hitting innocent bystanders now. Three automatics in the black, speeding car spoke in unison. A fusillade of bullets lashed through the night.

One of them ripped across the top of the cab, tearing the fabric into a ribbonlike streak. Another plucked at the cloth of the Agent’s coat. In a moment now that centering fire would bring death and destruction. Men in the Secret Service were taught how to shoot.

The Agent’s eyes were darting bleakly about. There was a patch of dense leafless shrubbery ahead. The road made a long curve by it. Suddenly the Agent reached forward, gripping the driver’s arms. The driver cursed in fear, tried to struggle free. The Agent held on like iron, kept the cab headed for the shrubbery.

The cab lurched off the concrete, taking the low embankment in a careening, rocking bound. Its wheels struck frosted turf, squealed, and bounced. One tire struck a sharp lump of ice and blew with a report like an exploding bomb. The cab slithered around, went sidewise toward the bushes. It would have turned turtle if the tough stems of the shrubbery hadn’t cradled it. It ploughed in amongst them while the driver cried out in fear, flinging his hands before his face.

For ten feet it crunched on, breaking branches right and left, ploughing like a tractor through wheat. Then the tough shrubs won out. A cylinder head in the racing engine gave way. The engine came to a clanking, groaning stop, and the cab slid to a standstill.

Blonde Nina was on her knees on the floor, her dress around her silk-stockinged legs. Agent “X” jerked the cab door open, drew her out. The driver was scrambling out also, howling in fear.

A sudden jet of gasoline escaping from a severed feed line bathed the hot cylinders and leaped into a sheet of flame. Agent “X” pulled the woman away just in time. Flame enveloped the cab, crackled and snapped in the bushes, making a blinding intensity of light.

He heard the squeal of madly-applied brakes on the concrete roadway behind. The momentum of the pursuing car had carried it three hundred feet beyond the spot where the cab had lurched off the road.

The Agent clutched at the woman’s arm, pulled her through the bushes. They ploughed ahead with the shrubbery tearing at their clothes. Then they came to an open space and ran on till they reached a path. Far behind them the flames of the burning cab made a glow like a torch. Miniature figures, silhouetted against the leaping flames, ran up and stood about. Others beat among the bushes.

The Agent would see later that the cab company was repaid and that the driver was exonerated. He didn’t like to drag innocent persons into his dangerous exploits. This time it had been unavoidable.

THEY ran on across the park till they had reached a safe distance. The woman began tucking in strands of loose hair and straightening her disarranged dress. The expression of fear left her face. She was resuming her former tigerish poise.

“Very good, Armand,” she said. “I must congratulate you even if you are a murderer and a thief.”

Then suddenly, she cried out and looked at her arm. Crimson was dripping from a superficial wound above her wrist.

“I will take you to your home,” he said, “or wherever you are staying.”

He signaled another cab at the avenue across the park. Nina gave him the address. They were silent now as the cab rolled along, Nina nursing the wound in her arm and darting analytical glances at him.

She had leased a small apartment in the mid-town section and, when the cab stopped, she spoke to Agent “X.”

“You may come up,” she said. “We will make our arrangements now. There is still the matter of how much you intend to pay me.”

He ignored her words, but followed her into the building. They ascended to a suite on the third floor, entered it, and closed the door.

“Let me fix your wound,” he said.

He got water, helped her bathe it, tied it up, then rose.

“Where are you going?” she asked.

“Away, my dear Nina. We have had an exciting and pleasant evening. Now it is time to part.”

With a tigerish leap she sprang forward, clutched her hand bag, and drew the gun out.

Viciously she jabbed its muzzle toward him. He stood smiling, lighting a cigarette.

“I repeat — it is time for us to part.”

“You can’t go,” she screamed. “I’ll kill you and hunt for Roemer myself.”

“You are an impulsive woman, Nina — too impulsive for one of your vocation.”

He turned toward the door. Behind him the trigger mechanism of the automatic clicked emptily four times. She had tried to pump a stream of bullets into his back — tried to murder him.

He turned and bowed.

“I took the precaution,” he said, “of removing the cartridges while we were having our little ride.”

She gasped and crouched, glaring at him.

“You will be sensible,” he continued, “and wait till I have completed negotiations with a certain party. If you call the police or kill me now, all will be lost. But I see that you are not going to be sensible, dear Nina. You are shockingly intoxicated with the greed for gold. Therefore—”

He reached forward, yanked the cord of the telephone out of the wall, flinging the instrument down. Then, with a mocking bow, he opened the door and walked out, taking the key from the lock. Outside, he locked the door and slipped the key in his pocket. It would be some time before she got out, and meanwhile he had much to do.

Chapter IX

IT was late, nearly one-thirty; but the Agent chartered another cab and gave an address on Twenty-third Street. The taxi sped downtown. It drew up in the middle of the block before an apartment house.

The Agent paid the driver, then, before entering the building, stepped among the shadows on the opposite side of the street. Two walls came together here forming a dark recess. From it, unobserved, he could look up at the side of the apartment. Many windows were still lighted. There was a light in a window on the sixth floor.

The Secret Agent moved his lips and gave a strange, low whistle. It was melodious yet eerie with an oddly ventriloquistic note. No one standing even a few feet from “X” could have told where it came from. It seemed to fill the whole air and it echoed in both directions along the quiet street.

The shade of the window with the light in it on the sixth floor moved upward. The window was raised and a girl’s head suddenly appeared. From the street her features were visible. She was no more than an enticing silhouette against the light in the room behind her. She looked searchingly up and down the dark block as the Agent repeated the whistle. Then, seeing nothing, she withdrew and closed the window.

The Agent strode quickly into the apartment building, ascended in the automatic lift, and pressed the button of suite No. 6B.

The click of high heels sounded on the parquet flooring inside. The door opened, and the girl who had looked out the window stood framed in the threshold. She, too, was blonde, like Nina, but she was of an altogether different type.

The small, warm oval of her face held sweetness and poise. Her blue eyes were frank, their keenness softened by long, silky lashes that swept to her cheeks. The gleaming wealth of her hair, alive with the glow of the light behind her, made a sunny halo around her head, blending with the creamy whiteness of her neck. Her petite figure was draped in clinging lounging pajamas that revealed its shapeliness. A coolie coat had been flung over the pajamas. She drew this hastily around her and looked questioningly at the man in the doorway.

Her eyes showed no recognition, but her soft warm lips seemed ready to break into a smile. Unable to penetrate his disguise, she was waiting for a signal. He gave it to her, making a motion in the air with his finger — the sign of an X.

Her expression changed instantly. The man before her, whose disguise was so perfect, had revealed his identity by that mysterious gesture. His whistle had told her he was on the way. Now he stood before her — Secret Agent “X.”

The girl’s blue eyes showed infinite respect. She had never seen the real face hidden behind his thousand disguises. He had fooled her again and again, tested out dozens of make-ups on her. Only on rare occasions, when the old wound in his side gave him a twinge of pain and he pressed his hand to it in a characteristic gesture, had she known who he was without being told by some sign or symbol.

There were reasons for the respect and friendship she felt for this strange man. He had been a friend of her father’s — the father who was a police captain slain by underworld bullets. She knew that Agent “X” waged ceaseless warfare on that underworld that she hated and despised.

In her capacity of newspaper woman, a reporter on the Herald, she was often able to help him indirectly, give him information about people, or carry out some order that would contribute to the capture of a criminal.

It made her happy to do this, even when by doing so she got into danger herself. And, being human and feminine, she was curious about the real man behind those brilliant disguises. There was in her something that responded to the strange magnetism, courage and daring of Secret Agent “X.” She sensed that death was always at his elbow. She knew there was little hope of any romance between them. But by comparison with him, other men seemed tame, uninteresting.

SHE walked ahead of him now into the comfortable living room of the apartment she maintained by her own hard work.

“Sit down,” she said. “I’ll get you some cigarettes.”

The Agent was silent, but his strange burning eyes followed her. She was a girl in a million, as clever and brave as she was beautiful.

“The harvester has been at work,” he said abruptly.

Betty Dale turned and looked at him. Agent “X” seldom spoke like ordinary men. There were generally innuendoes, subtleties, and double meanings in everything he said. His speech was as mysterious as his person.

He was holding a sheaf of bills in his hand now. She saw many bank notes of high denomination. He flipped them on the table.

“For victims of the wolf,” he said.

She knew at once what he meant. The money that the Agent took from criminals was used to help the victims of criminals. Betty Dale saw to that. Simply, unpretentiously, she distributed what he gave her among people whom crime had in some way left destitute. The wives and small children of men serving prison sentences. Widows and orphans of murder victims.

Was it only to bring her money that the Agent had come?

She saw that tonight he seemed tense and ill at ease. There was an odd light in his eyes, restlessness in the movements of his body.

“Is there any other way I can help yon?” she asked quietly.

He shook his head, blowing quick jets of smoke through his nostrils.

“Ghost fingers are better dealt with alone.”

The girl’s face blanched at this. Her eyes widened.

“You are fighting the Spectral Strangler then,” she said. “There’s danger — terrible danger in that. Four people have been killed already. Be careful for my — for every one’s sake.”

The Agent nodded grimly.

“The trail is getting warm,” he said.

She came closer and spoke again.

“I’ve read about those murders. Every one is talking about them. They are ghastly, unthinkable. I was going to ask a favor of you — but now, now I won’t.”

For Betty to ask any sort of favor of him was so unusual that the Agent stared at her keenly. Then he spoke quickly.

“A girl with sunny hair and sunlight in her heart has helped me often,” he said. “There are debts that it is a pleasure to pay back. Your favor, whatever it is, is granted.”

A flood of color swept into Betty Dale’s cheeks. For a moment she turned her face away, hiding the sudden surge of emotion she didn’t want “X” to see. Love must never come between them, never interfere with his work. And sometimes in his presence, when he showed the admiration he felt for her, she had to fight love down.

“I was going to ask,” she said huskily, “that you go with me to Colonel Gordon Crandal’s party tomorrow night. The paper wants me to cover it. There’s the society angle — and there’s something else.”

“Something else?” he echoed, caught by the sudden frown on her face.

“Yes,” she said. “Colonel Crandal is rich, aristocratic — and the Crandal jewel collection is famous. He’s received threats from some criminal who plans to steal them. The Herald was tipped off tonight. There’ll be lots of detectives at the party. The police commissioner himself will be among the guests.”

“Tell me more about this criminal,” he said. “What crook plans such a daring robbery?”

“No one knows. He calls himself the Black Master.”

It was Agent “X” who paled this time beneath his disguise. For a moment his long thin fingers tightened over his cigarette, squeezing it until tiny golden shreds of tobacco spilled to the floor.

“The Black Master?” he echoed harshly.

“Yes — do you know of him?”

He did not reply, but the vivid light of deep emotion sprang into his eyes. He was silent for seconds while the girl studied his face. Then he spoke hoarsely.

“Only death could keep me away from Colonel Crandal’s party, Betty. You are assured of an escort who will try to match in gallantry the beauty of the girl he accompanies.”

Chapter X

THE Crandal name was an old and honored one. The Crandal mansion, owned now by Colonel Gordon Crandal, a reserve officer with a distinguished war record, was one of the city’s show places. It occupied nearly a whole city block. Great iron gates closed the street entrance except at such times as the owner chose to admit guests.

Tonight was one of those times. The many windows of the Crandal mansion were brightly lighted. An orchestra was playing seductive dance music. The huge ballroom, where presidents and visiting royalty had danced, was open, its furniture dusted, its ancient crystal chandeliers glittering impressively.

The end of prohibition had brought old-time gaiety back. The portraits of long-dead ancestors in tarnished frames seemed to smile down in approval at the handsomely-dressed company. Men were there in tail coats and dinner jackets. Ladies in low-cut evening gowns. Radiant debutantes were attired to reveal charms that would lure hesitant bachelors into the bonds of matrimony.

Faithful old servants of the Crandal family moved silently about the polished floors, trays of cocktails in their blue-veined hands. They seemed as much of an inheritance as the house itself.

Betty Dale and her escort came shortly before nine — shortly before the fashionable hour so that Betty, because of her newspaper work, wouldn’t miss seeing the arrival of the more impressive guests.

She wore blue slippers and a clinging blue dress, complementing the gold of her hair. A white evening wrap was thrown about her shapely shoulders. Her loveliness rivaled that of any blue blood present.

Girls cast envious glances at her as she entered. Men paused to stare in admiration. Her escort came in for a share of attention, too.

Tall and immaculately dressed in formal evening clothes, his face had the lean, healthy look of an out-of-doors man. It was darkly tanned. His hair swept straight back from a strong forehead. His temples were slightly, becomingly gray.

Betty Dale introduced him to those of the guests she knew.

“I want you to meet Clark Manning, the explorer,” she said.

She spoke convincingly. People mumbled that they had often heard of Clark Manning. To admit that they hadn’t would have seemed both rude and ignorant. A gushing lady spoke admiringly of Manning’s travel books — taking care not to mention any particular titles. Manning seemed like a man worth cultivating. His burning, deep-set eyes were strangely compelling and mysterious.

A friend of Betty’s brought Colonel Crandal up to them. The scion of the ancient family was in his late forties, tall, gray-haired, poised. He was still a bachelor and eager, hopeful debutantes flocked around him like satellites around a star.

He acknowledged his introduction to Betty Dale and her escort, Secret Agent “X,” now posing as Clark Manning, explorer.

The colonel’s swift, experienced eyes appraised Betty from her trim little slippered feet to the sunny gold of her hair. Then he spoke debonairly, asked her to dance, and bore her off, leaving a half-dozen disappointed young ladies in his wake.

The girls looked to Secret Agent “X” for consolation. They begged him to tell them about his explorations. But he shook his head modestly. In a few minutes he edged away and strode off to reconnoiter by himself.

HE studied the smiling, gay faces around him. Would they be so smiling, so gay if they knew that the threat of the Black Master hung like an evil shadow over this house? Wouldn’t their bright laughter turn to whispers of ghastly fear if they knew that the man who had threatened Crandal was the murderer who killed with invisible, choking fingers?

Among the guests were quiet-faced men in dinner jackets — men who seemed to have no part in the festivities.

These were agency and police detectives detailed to watch and protect Crandal’s famous jewels from the menace of a daring criminal. But even they, “X” felt certain, didn’t know with whom they were dealing. They didn’t know that the Black Master and the dealer in swift, strangling death were one and the same.

Agent “X’s” gaze was hawklike. Was it possible that the murderer of Scanlon and those others was somewhere in this brilliant gathering?

His eyes wandered from face to face. He saw the city’s tall, suave police commissioner talking to a group of ladies, thrilling them with tales of his police experiences, his successful contests with criminals. Before this night was over the commissioner might have something else to think about — something too ghastly perhaps to relate as drawing room conversation.

Then Agent “X” gave a sudden start.

More guests were arriving. He saw a flash of light on blonde hair. A woman in a flame-colored evening gown came through the ballroom door. She moved tigerishly, sinuously across the floor, a tall, dark man at her side. She was smiling radiantly — smiling with her red lips, but her eyes did not smile. They had the cold, appraising look of an adventuress.

“Nina!” whispered the Agent tensely under his breath.

It was a shock to see her here — a surprise. Yet, staring around at the mixed assemblage, he saw that her presence, was not altogether out of place.

Whispers had it that Colonel Crandal planned to run for the legislature. People of all types and from all walks of life had been invited to this party. A politician and a city commissioner hovered around the punch bowl. A night-club hostess leaned on the arm of one.

Beyond them, fat and baggily dressed, was Nick Baroni, a big shot in the days when gangdom rode to wealth and power on a flood of illegal liquor. He had paid his income taxes, escaped jail. He had reformed, so rumor had it, and was spending his money to gain entree into society. A thin veneer of social polish hid brutal instincts that slumbered behind his oily, massaged face. He was balancing a cocktail glass in fingers that had once tensed around the vibrating trigger of a Tommy gun.

The Secret Agent’s lips curled.

Then his eyes swiveled back to the woman in the red dress. He edged close, lighting a cigarette, and heard Nina and her escort introduced.

“Piere DuBrong and the Countess Rocazy,” the lady who presented them said.

Nina was carrying it off well. An elaborate coiffure had been artfully molded to soften the lines of her face. Her nails were stained a vivid crimson. She held a small fan in her hand, pressing it close against her white bosom. She was capitalizing on her exotic charm, playing on the gullibility of social climbers to whom a European title was a thing before which to bow down and worship. But Agent “X” was not impressed. He believed that her title was bogus.

The man with her, Piere DuBrong, had the alert hungry look of a questing hawk. His glittering eyes indicated a keen, acquisitive brain. The two appeared well matched.

But why were they here?

Secret Agent “X” made discreet queries. Who was the charming countess? Who was the tall man with her? He learned that DuBrong was attached to the embassy and that Countess Rocazy was a friend of his, a lovely woman just over from Europe who could speak excellent English.

On the surface that explained matters. But Agent “X” wasn’t satisfied. His sense of impending menace deepened. The gaiety of the gathering impressed him now as gaudy beauty hiding something darkly evil. The bright skin of a poisonous serpent! A blood-hungry beast concealed in a bed of gay flowers! Nina Rocazy was like that — a tigress cloaking her claws behind velvet fur until the moment came to spring.

She and her escort had separated now. Agent “X” was introduced to her and even danced with her. He felt the strange undercurrent of drama as he held the woman in his arms. What would her reactions be if she suddenly learned that her dancing partner was the same man who had accompanied her on that wild taxi ride which had so nearly been fatal? What would she say if he told her he was the same man she had tried to kill and who had locked her in her apartment?

He gasped at her audacity when she asked if he thought it would be possible to see the Crandal jewels.

“I have heard so much of the riches of Americans,” she said. “Jewels are riches that even we poor women can understand. They attract us as children are attracted to bright, pretty baubles. There must be other women here who would like to see them, too.”

Agent “X” nodded. She did not understand the mocking light in his eyes.

“Such a woman as you would be doubly appreciative,” he said.

Beneath her smile, lines of avarice showed. Money, the things that money could buy, were the gods she lived by. But would she have cheek enough to make such a request to Colonel Crandal?

“There has been a threat,” he said. “A criminal has announced that he intends to steal the jewels.”

He watched her face, but her hard eyes were inscrutable. She shrugged.

“Colonel Crandal is a brave man. He will not fear threats.”

THE dance ended and he left her. But he followed her through the milling company and saw her cleverly insinuate herself into the group around the colonel. Smiling radiantly, acting as though the impulse had suddenly come to her, she asked if she might see the famous gem collection.

For a moment Colonel Crandal’s face showed surprise. Then he smiled and nodded.

“Certainly, countess, I’ll have the jewels brought down. All of you can see them then.”

Agent “X” edged close. He heard the police commissioner object.

“What about the threat of that crook?” the commissioner asked. “Isn’t it going in the face of Providence to bring them out tonight?”

Crandal made a gesture with his hand.

“That’s what your men are here for — to give protection. And a lady has requested that they be shown.”

The commissioner flushed and nodded.

“Very well,” he said.

Crandal whispered the combination of the safe into the ear of an old and trusted butler who had been with the family forty years.

“Go get them, Wilmot,” he said. “But be careful.”

The butler protested.

“I wish, sir, that you would come with me. If anything should happen—”

Crandal gave the man a push.

“Do as you’re told,” he said.

Three detectives followed the butler, after a low-voiced conversation with the commissioner.

In ten minutes the butler returned carrying a square leather box in his hands. His fingers were trembling as he set it down.

“There, sir,” he said, and there was a note of vast relief in his voice.

The guests crowded around tensely. Crandal opened the box, exposing the glittering collection of gems that reposed on a cushion of black velvet.

There were rubies that gleamed like drops of freshly fallen blood, emeralds as green as polar seas, sapphires blue as the sky, diamonds that reflected sparkling prismatic lights and gave off rainbow colors. Many of them had come from the crowns of former kings and queens.

Crandal held them lovingly in his hand, then passed them about.

Nina took a diamond necklace and held it in trembling fingers. She placed it against her neck, let the cold stones touch her skin. Her eyes were dark with greed. She seemed reluctant to give it back.

But the other guests were nervous, holding the jewels gingerly, or refusing to take them at all. They appeared to breathe easier when the gems had been exhibited and put safely back in their box. The old butler picked the box up and solemnly bore it away with his escort of detectives. The police commissioner wiped a perspiring face, and Secret Agent “X,” watching Nina’s every movement, wondered what was going on in her mind.

The butler had taken the jewels up a flight of broad stairs to a second-floor room. Several detectives hung around this stairway for minutes after he had disappeared. The others remained with him on the floor above.

The dancing began again. Liquor flowed freely. The guests and even the police commissioner appeared to relax. But Agent “X” stood tensely staring around. At the moment he could not see Nina, Piere DuBrong, or the pudgy-faced Nick Baroni. He pushed his way through the crowd watching the dancers until the blonde head of the Countess Rocazy came in view. She was in the arms of the politician. He looked about for the others; then suddenly whirled.

A stumbling, horrible figure had appeared at the head of the stairs. It was Agent “X’s” hoarse exclamation that stilled the music and attracted the attention of the other guests.

A ripple of tense excitement passed through the assemblage. It increased with the speed of a spreading grass fire. Talk ceased. Laughter died away. All eyes were turned toward the stairway.

The man at the top of them was one of the police detectives. He seemed to be trying to say something. He was waving his arms, staring toward them. Then his hands, clawlike, went to his throat.

He reeled, staggered, clutched at himself. One choking, terrible cry came from his lips. It was silenced as though by the jerk of an unseen noose. The man appeared to be fighting invisible fingers that were wrapped around his neck.

He twisted, swayed, lurched forward. His feet slipped on the top step.

Then, while women screamed and men shouted hoarsely, he plunged headfirst down the slippery hardwood stairs. His body landed with a thud on the rug below. But the man had ceased his struggles now. His face became purple, the terrible livid purple of an overripe plum, the hue which had mottled the dying face of Bill Scanlon. His lips were drawn back in a mirthless, hideous grin. From between them his swollen tongue protruded, mocking, horrible.

While men and women in the room stood frozen with fear, too scared to speak or move, too weighted with horror to do more than breathe, there came a fearful explosion somewhere on the floor above. It rocked the house, rattled the windows.

A cloisonné vase dropped off a shelf and rang against the floor. Another of porcelain shattered to fragments as it fell. In the crowd, close to the Secret Agent’s side, a woman screamed and fainted. Then pandemonium broke loose.

Chapter XI

SO terrific was the explosion on the floor above that it seemed as though a bomb must have gone off. Plaster fell from the ceiling. Crystal pendants from the old chandelier followed it in a clattering, tinkling cascade.

Men and women made a wild dash for the doors, jostling each other, crowding, shouting in a mad stampede. Their fear made them forget that they were ladies and gentlemen.

A paunchy man in a dress suit with glittering diamond studs brushed Betty Dale aside with a sweep of his fat arm and charged ahead like a frightened bull.

Agent “X” saw the man’s action from the corner of his eye. His lip curled in contempt. The man lurched by him and the Agent thrust a quick foot into his path tripping him, disregarding the fact that the man was the president of one of the city’s leading banks. The bank official skidded along the floor carrying a rug with him.

The police commissioner was shouting, too, trying to stem the tide of panic. His voice boomed out. The frenzy began to subside.

Secret Agent “X” leaped up the broad stairway, his eyes burning with excitement. Three detectives, freeing themselves from the milling crowd, followed him.

At the top of the stairs there was a long hallway. Agent “X” looked down it. Another figure lurched into sight. It was the old butler, the man who had carried the jewels down for the guests to see. The butler’s fingers were clawing at his throat. He collapsed on the floor as the Agent neared him. His face, too, had the ghastly livid hue of strangulation.

Debris, and the broken panels of a door showed the location of the explosion. Secret Agent “X” needed no one to tell him it was the entrance to the jewel room.

The door was hanging loosely on its hinges. He thrust it open, stepped inside. The force of the explosion had shattered every light bulb. In the gloom he almost fell over another form — another detective.

One of the plain-clothes men behind him flashed on a light. “X” saw then that the man at his feet was dead, too. He had evidently fallen before the explosion had taken place. His body was twisted grotesquely, his features mutilated beyond recognition. Death and horror had struck here.

“The safe’s been blown,” said the detective behind “X” harshly.

The beam of the man’s flash light was focused on the heavy iron box across the room. It was twisted out of line now, its sides bulging, its doors blown off.

“Soup!” said another detective. “A bungling job, too. They used enough nitro to wreck a house.”

With drawn guns, both men leaped across the room, running to a window which was open. It gave on a balcony. They turned their lights down on the lawn beneath. Secret Agent “X” heard them cry out. Peering over their shoulders, he saw a fourth huddled form on the icy turf. The detective stationed to patrol the grounds had been killed along with the two others.

Guests, taking courage, now that the police were going to the scene of the explosion, were coming up the stairs, crowding into the hall.

Crandal came into the room, two friends with him. The millionaire’s face no longer wore its look of easy assurance. He was tense and pale.

“The jewels are gone,” he said hoarsely.

He seemed to forget the dead man lying at his feet, the other men outside. He was staring wide-eyed at the safe.

In front of it was the black leather case that had contained the jewels. It was empty, battered and broken by the terrible force of the explosion. There wasn’t a jewel in sight.

Colonel Crandal leaped to the window. He stood speechless, staring out.

The police commissioner appeared in the doorway, a group of guests, including Piere DuBrong and Nick Baroni, with him. The commissioner’s collar was torn. His hair was on end. He had been fighting to stop the panic downstairs. He said:

“You’d better go down, Colonel. You’d better go and quiet your guests. Tell them it’s over now. That criminal made good his threat.”

There was bitterness, defeat, in the commissioner’s voice.

“This has been a terrible night, Colonel,” he continued. “Three of my men gone. They tell me MacCarthy outside was killed, too.”

THE Secret Agent was listening. His burning eyes were swiveling around the room, staring at the safe and the window. The killer had wiped out clues, wiped out any possibility of identification by leaving a trail of death behind him.

The Agent’s gaze came to rest on the faces of DuBrong and Nick Baroni. They both appeared shaken and terrified. But were they? The Agent was baffled. It was as though the Black Master was a being as intangible as the murder weapon he used. Agent “X” stared out the window off across the ice-coated lawn. The commissioner issued a harsh order to those of his men who were left.

“Go out and hunt around. Get some clews that will help Burks.”

Hatless and coatless, the Agent dashed out on the lawn. The glow from the lighted windows on the first floor shed ghostly radiance. He supplemented their glow by lighting matches. The detectives came with their flash lights.

But Agent “X” had discovered in his first brief examination of the lawn how hopeless it was to look for clews here. The ground was frozen as solidly as rock. The short turf was matted with ice. Its glass-smooth surface showed no tracks. A hundred men might have walked over it.

He moved up to the dead detective. The man’s distorted features showed that the Spectral Strangler had struck him down also. What horror had he seen out there in the semi-darkness? His bloodless lips would never tell now.

Down on his hands and knees. Agent “X” examined the ground around the form of the slain detective. For a moment he bent close, then flattened his palm, rubbed it over the icy coating. Something sharper than ice pricked his skin. He drew his hand up, looked at it. Tiny particles of glass were clinging to it. They were even more fragile than the shell-thin globes of electric light bulbs. A detective came up to his side.

“What’s the matter? What the hell are you looking for, mister?”

The Agent held his hand out.

“Glass,” he said quietly.

The detective swore harshly, took an empty envelope from his pocket.

“Give it to me,” he said.

The Agent passed the glass slivers over. He had forced the police to share a clew with him. It was only fair that he share this one now with them. He believed he understood its significance, but he doubted that it would lead anywhere.

A police siren rose into a moaning wail out in the street. A car turned into the driveway of the Crandal home and drew up before the big entrance-way.

Secret Agent “X” went back into the house. He was there when Inspector Burks of the homicide squad met the police commissioner. The two went into a whispered consultation for a moment; then the commissioner held up his hand, addressing the frightened guests.

“There’s a criminal you’ve all heard of — a criminal I’ve reason to believe struck tonight, stole Crandal’s jewels, and killed these men. I’m referring to the man who masks behind the name of Secret Agent ‘X.’ It is my belief that he and the Black Master are one.”

Betty Dale came close to Agent “X.” Her eyes were dark with anxiety.

“We’d better leave,” she said. She wasn’t thinking of her newspaper work; she was thinking only of the Agent’s safety.

His smile reassured her.

“There is work for the lady scribe,” he said. “She must stay. But far places call an explorer. He has a rendezvous at midnight.”

He looked at the great clock against the wall. It was after ten now.

Some of the guests began to leave. An air of gloom and horror had fallen over the house. The atmosphere of festivity was gone.

Other police cars joined the first one in the drive. Fingerprint experts, Bertillon men, official photographers, the medical examiner and his assistant, and a detail of men from the bomb squad arrived. It seemed that every detective in the city was pouring into the Crandal home.

SECRET AGENT “X,” under the guise of Clark Manning, explorer, slipped quietly away. There were deep suspicions in his mind. He intended to investigate Piere DuBrong and the gangster, Nick Baroni. Was it only coincidence that they were there when the robbery took place? But he had a rendezvous at midnight. It could not be postponed. And a question burned in his mind. After such a fiendish and daring crime, would the Black Master still meet him in that silent, empty house that faced Bradley Square? If so, he had a plan worked out. He was ready tonight to take a desperate chance.

He drove quickly to his apartment on Jefferson Avenue, disguised himself as Greenford again. The spy was still unconscious, breathing peacefully in the closet.

The streets were deserted when “X” reached the square. It seemed a place of ghost houses. There was only one light burning. That was across the square in the beer saloon, dimly seen through the jumble of playground equipment. The rusty chain of a swing creaked in the night wind as the Agent passed it. It made a sound like a body swinging on gallows.

With the faces of the three slain detectives and the butler still before his mind’s eye, the horror of the empty house seemed to have deepened.

There was not only the chill of mystery as he climbed the steps now. There was a living threat. The brooding, towering menace of death.

He pulled the ancient bell handle, half expecting that this time there would be no result. How could the man who called himself the Black Master be everywhere at once, unless he was the very spirit of evil itself?

Echoes clattered inside the house. A minute passed. Then again the lock of the door clicked and the old door swung open, moved by unseen hands. The Agent entered quickly. As he moved along the black hallways, he struck a match and noticed something that seemed to add to the ghostliness. His own tracks still showed in the dust. They had not been disturbed. There were no others beside them. It was as though he had entered a house peopled only with sinister spirits.

He was slightly ahead of time. He waited in the still top-floor room, waited till a clock somewhere outside boomed twelve strokes. Then suddenly there was a dry rattling in the room. For an instant it was horribly reminiscent of a snake or of some huge reptile uncoiling. Then the voice he had heard before spoke.

“The Black Master salutes you, Greenford. What is your answer? Speak loudly.”

Imitating Greenford’s foreign accent, the Secret Agent spoke. It seemed as though he were talking to the blank walls of an empty room. It was uncanny, spine-chilling. His own voice reechoed in his ears.

“My government is prepared to pay a large sum for what you have. It is prepared to pay a hundred thousand dollars.”

There was an instant of silence, then a harsh laugh broke out. There was bitterness, mockery, contempt in the laugh.

“A hundred thousand dollars! A hundred thousand! You come here and offer me a hundred thousand — for something that will affect the destiny of nations? For something that holds in it the secret of death itself?”

The Agent injected excitement into his answer.

“Give me time then. Perhaps I can make them understand — make them pay more. Perhaps I can raise it to two hundred thousand!”

Again the mocking laughter filled the room.

“Two hundred thousand! The thing that you seek to buy has already snuffed out the lives of eight people. A nation could fall before it as well.”

“Eight people!” The Agent gasped the two words, baiting the hidden voice on.

“Yes, eight people. When you read the papers tomorrow, you will understand.”

“What is your price then? What shall I tell my government? There must be some reason in this.”

“A million dollars,” the voice said. “That is my price today. If I am goaded too far, it might rise. Those who do not pay my price will regret it. Tell your government that.”

“It is too much — it is impossible,” said the Agent. “With governments bankrupt, with revenues lessening, how can you expect so much?”

“Fool!” said the voice. “I ask less than the price of one submarine, the cost of one dirigible. You have seen how I can strike. Beware.”

“Give me one more chance,” the Agent said. “I’ll see what I can do.”

“Tomorrow then — at the same time. It is your last chance. I cannot deal with fools and bankrupts. There are other countries that will pay.”

The voice ceased speaking. The room was still. The Agent asked another question; but the walls echoed his own voice back. He went into action suddenly, took a short-bladed, gleaming tool from his pocket.

He moved sidewise, ran the sharp tool down the wall, ripping at the paper. It was from there he decided that the voice had come. Was there a secret room beyond, or—

He gave a harsh exclamation. The thick paper had come free. Behind it, sunk in the wall, was the bell-shaped outline of a radio loud-speaker. There was the small circle of a microphone below it. He ripped at the plaster feverishly, saw the compact radio mechanism behind it, and uncovered antenna wires leading to the roof.

The mystery of the voice in the room was solved. But the Black Master was as much a mystery as ever. The trail of the horror killer led on — into a fog bank of terror, eeriness — and doubt.

Chapter XII

AS he left the house he stopped for an instant to examine the door in the lower hallway. The mechanism that operated it was concealed. But he found a wire attached to the old bell cord, leading upward. He pulled this wire and waited. Seconds passed and the door opened. He understood then that the radio impulse sent out from the same station as that of the voice which had addressed him was responsible for its mysterious movements. Battleships and airplanes had been operated by radio control. The Black Master had installed radio controls on a door.

With burning, intent eyes he descended the steps and moved along the street. Again he had the uncanny sense that he was being followed. He paused with a cigarette in his hand, and, before lighting it, stared back through his cupped fingers.

A dark, flitting shadow moved into an areaway behind him.

As though he had seen nothing, the Agent turned and continued his way along the street. But at the next corner he ducked out of sight into a doorway. Skilled himself in all the arts of shadowing, he planned to turn the tricks on his shadower.

Standing in the blackness of the doorway, he looked back. A small man came around the corner, moving with quick, furtive steps. The man stopped suddenly as he saw that the block ahead of him was empty.

For a moment the street light fell upon his face. His features had a vicious, pallid cast. He looked as though drugs had ravaged his body, made him a depraved and inhuman wreck. His eyes were glittering with feverish brightness, his face muscles twitching. Suddenly he retraced his steps, seeming to sense that he had been tricked.

The Secret Agent waited a moment, then came out of his hiding place. Walking close to the side of the buildings he followed the small man ahead. So deft and sure were his movements that he seemed no more than a blending shadow.

He caught sight of the small man again as he rounded the corner. From then on it was the other’s turn to try and shake off pursuit.

He seemed to think he had. Six blocks from the square, he came out into the light, walked across the street, and entered a telephone booth. The Agent, watching from the other side, could see him making a call.

Then the utterly unpredictable happened. A movie house next to the drug store disgorged its audience abruptly. The street became clogged and choked with jostling people. The hophead slipped out of the booth. His small height made it impossible for any man to see him.

The Secret Agent elbowed his way quickly through the crowd. But, when he reached the other side of it, the small man was gone.

Agent “X” frowned grimly, bitterly. Twice tonight the law of averages had been against him. Twice he had been disappointed. His search of the room in the house at Bradley Square had yielded nothing but the discovery of the concealed microphone and loudspeaker. Now circumstances beyond his control had made him lose the man he was shadowing. It was a thing that happened to the most skilled man hunters in the world. But the Agent refused to accept defeat.

A swift plan came to his mind. The investigation of Nick Baroni and Piere DuBrong would take time, days even. But perhaps Greenford could tell him something about the latter, give him a quick lead.

SWIFTLY he returned to the St. James apartments on Jefferson Avenue. Greenford was still there. With the spy unconscious in the closet, Secret Agent “X” removed the make-up that impersonated him and again resumed his disguise of a middle-aged man. It was almost time for the effects of the anesthetic he had administered to wear off. But in any event he would have found means of bringing Greenford back to full consciousness.

He injected a liquid containing extracts of adrenaline, strychnine and digitalis into Greenford’s arm. A large dose of it would have been fatal. But the Secret Agent was a master of pharmacology.

The hypo injection acted immediately on Greenford’s heart It brought him out of the quiet of artificial sleep with the abruptness of an electric shock. He sat up, twitching and glaring about. His eyes fell on the Agent and for a moment he tried unsuccessfully to talk. It was some seconds before he found the power of speech.

“You can’t hold me like this,” he said harshly. “I’ve got an appointment tonight.”

The Agent smiled. Greenford’s appointment was already more than twenty-four hours overdue. The man didn’t know he had been sleeping a day and a night.

“What time was it scheduled?” the Agent asked.

“Twelve o’clock.”

“It’s nearly one now!”

Greenford rose to his feet. Fear had come back into his eyes. He looked at Agent “X” strangely.

“Who are you?” he demanded again.

The Agent shook his head. He was staring at Greenford, and he saw Greeaford’s hand go to the pocket where he had placed the telegram of the Black Master. A startled, worried look came over Greenford’s face.

“You stole it,” he hissed.

The Agent bowed.

“I saved you from an unpleasant interview with a dangerous man,” he said.

Greenford made a snarling sound and clenched his fist.

“You’re going to tell me who you are and why you are meddling in my affairs.”

The lightness left Agent “X’s” voice.

He gazed at Greenford in a way that made the other man tremble. There was burning power in Agent “X’s” eyes. They seemed to have foresight, uncanny magnetism. They seemed to bore into Greenford’s very soul.

“Perhaps you’ll tell me why you bribed Cora Stenstrom to betray her employer?”

“I didn’t — I didn’t,” said Greenford in a sudden frenzy of excitement.

“She was in your pay. Do you deny it?”

Greenford’s face twitched, his eyes wavered. It was plain that he had been lying. Suddenly he burst forth in a torrent of denials, even before the Agent had accused him.

“I didn’t murder her,” he shrieked. “She was going to tell me what I wanted. She was going to phone me when all was ready.”

“You mean you paid her to leave the window open!”

“Yes — yes, I did, but it wasn’t I who killed her.”

“No,” said Agent “X” sternly. “Another and greater scoundrel preceded you. He took advantage of the path that you had made easy.”

“I know it,” said Greenford. “My God — who was it?”

“The Black Master,” said Agent “X” softly.

He watched Greenford. He could see by the spy’s expression that the name meant nothing to him. That telegram calling him to Bradley Square was the first time apparently he had had any dealings with the master murderer.

“Who is he?” asked Greenford trembling.

THE Agent was silent. For seconds his burning gaze rested on the man before him, until Greenford could stand it no longer.

“What are you going to do with me?” he demanded.

“Ask you a question,” said the Agent. “Who is Piere DuBrong, friend of the Countess Rocazy — the woman you once called Nina?”

Utter amazement overspread Greenford’s face.

“Nina! She is not in this country! She can’t be!”

“She is,” said the Agent sternly. “Answer my question.”

“I know nothing about DuBrong — I swear it! I haven’t heard of the man. Nina Rocazy is a dangerous woman — a viper. She is not a countess, but an adventuress — a woman seeking always to prey on men.”

The Agent’s eyes bored into Greenford’s. The spy seemed to be telling the truth. He spoke again.

“I’ve told you all I know. Now let me go.”

“I will,” said the Agent, “but on one condition only. It is that you leave the country at once. You made a mistake coming in the first place. Nothing awaits you here — except death.”

“You are threatening me!” said Greenford harshly.

“Not threatening — warning you. Will you leave or not?”

The Agent’s eyes held inexorable command. Greenford could not meet them.

“You have stolen my money,” he said. “My belt is gone.”

The Agent took out his wallet, extracted five hundred dollars, and handed it to Greenford.

“It is enough,” “X” said. “There’s a night plane to Canada. It takes off from the municipal field in half an hour. Your papers are in order — I have seen them. Take the plane and go before death prevents you.”

“My luggage!” said Greenford.

“It is too late now to recover it. The American Secret Service is on your trail. Operatives have unquestionably searched your room at the Sherwood. Menace hangs over your head. Your only chance of life is to leave instantly.”

Greenford shrugged resignedly.

“I will do as you say,” he promised.

But Secret Agent “X” took no chances. If Greenford tried to communicate with the Black Master all would be lost. He wanted to make sure that the spy kept his promise and left. When Greenford went to the street, Agent “X” stealthily followed. Then he frowned in anger and annoyance.

Instead of going to the flying field, Greenford took a taxi to the neighborhood of the Hotel Sherwood. He got out two blocks from it, walked toward it cautiously. Agent “X” followed, keeping on the other side of the street.

He saw Greenford walk furtively along the front of the hotel, passing the entrance three times without getting up enough courage to enter. There was a watchful man reading a newspaper far back in a corner of the lobby — a government operative. The Secret Agent recognized him; but it appeared that Greenford did not.

He lighted a cigarette, pulled his hat brim down, and started toward the main entrance a fourth time.

But he was destined never to enter.

He crossed the open space of sidewalk before the hotel, and it seemed that a noose was suddenly flung around his neck. He staggered on the pavement, clawed at his throat. Agent “X” heard one horrible choking cry and stared aghast at the drama that was taking place.

Greenford’s face was becoming purple — the fatal, livid hue that meant death at the hands of the Spectral Strangler.

Chapter XIII

AGENT “X” saw a stealthy figure moving across the face of the building. The figure was going away from, not toward Greenford, as would have been the case if it had been a casual passerby. It was the sinister hophead whom “X” had lost sight of in the theater crowd less than an hour before.

By disregarding Agent “X’s” warning, by failing to keep the promise he had given, Greenford had walked straight to his death. The emissary of the Black Master had slain him, thinking Greenford was the man who had shadowed him. He had been lurking in the vicinity of the hotel to destroy the life of a man he thought had tried to pry into the Black Master’s secrets.

The Agent darted in pursuit of the killer, resolved this time that he would not fail. He would shadow the hophead to his hideout and through him learn the identity of the fiend who employed him; for “X” felt certain that this drug addict was no more than a tool in the hands of the master murderer. As a criminal, he wasn’t of sufficient caliber to have plotted and carried out such a campaign of terror.

There was no chance of the hophead being lost in a crowd now. It was late. The streets were deserted. But because of this it was a difficult task to follow him without being suspected. The Agent depended somewhat on his make-up.

Behind him he heard someone come from the hotel entrance attracted by Greenford’s dying cry. He couldn’t help Greenford now. The man was beyond human aid, destroyed by his own greed and willfulness. He was the ninth victim in the terrible series of murders.

The Agent’s eyes were glowing with the light of intense concentration.

The hophead was walking purposefully now like a person who has accomplished an appointed task. He dived into a subway entrance, rode uptown, and got off in a section cluttered with theaters and cafés. Once again the Agent got a look at the man’s face. He saw that he had the features of a rat. There was cruelty in the feverish glitter of his eyes and the twist of his thin mouth.

The chase ended when the man disappeared into the servants’ entrance of a notorious night club — the Club Mephistopheles.

This club, the windows of which were curtained night and day, was known to the Agent. It was a place of evil repute, a place where gangsters hung out and where many criminals had made their headquarters. It was a place of vice and debauchery where “slummers” came also, social registerites who wanted to spend money freely and taste the city’s wild night life.

There were gambling tables inside. Here the underworld and the world of wealth and fashion rubbed shoulders. It had figured in the papers more than once. Bennie Pomarno, beer runner, had been slain here in the boom days of prohibition. In one of its luxuriously appointed rooms a well-known society matron had committed suicide after losing the last of her fortune at the roulette wheel. It was a club to which the Secret Agent had made it a point to get a card.

But dress clothes were necessary to gain admittance. Crime was hidden beneath the trappings of gentility. The Agent thought quickly, then went to an establishment near a dance hall where tuxedos could be rented. He hired one and entered the door of the Mephistopheles Club.

Though it was long after midnight, the activities inside had not begun to wane. The gambling rooms were crowded. The big dining room still held late diners. A jazz orchestra was playing sensuous music.

The Secret Agent strolled about eyeing the crowd that filled the place. He was waiting for the hophead to appear. Was he employed in this club? And if so in what capacity?

A red-headed, flashily dressed hostess came up to the Agent, but he waved her away. He recognized many faces. Here a society woman. There a crook with a police record. There a small-time politician seeking favor with the big shots of the underworld.

Then he drew back with a sudden, amazed intake of breath. He had glimpsed the fat form of Nick Baroni!

The gangster had evidently come straight here from Crandal’s party. Why? To seek solace in a familiar haunt after the terrible and nerve-racking experience at Colonel Crandel’s, or for some more sinister reason?

The pastiness of fear still showed on the big gangster’s face. The burning eyes of Secret Agent “X” studied him.

Could it be that Baroni was the man he sought — the terrible Black Master? The repeal of prohibition had made it hard for gangs to exist. Rivalry was more bitter. In the days when beer could only be had in speak-easies there had been enough money to support a score of big shots in the luxury that their gross bodies craved. But now this source of revenue had been abolished. The government and legitimate brewers were taking in what the gangsters had formerly regarded as their own. Rackets had narrowed down.

The bitter enmity of the gangs had deepened. They were ready to tear at each other’s throats like wolves; and the Mephistopheles Club was in a no man’s land between two gang territories.

THE Secret Agent stared and pondered. Baroni had his torpedoes with him now, flat-chested, pale-faced young men who talked without moving their lips and whose eyes were ever watchful; men ready to shoot at the drop of a hat. Rumors that Baroni had reformed were baseless. The fight over the city’s slot-machine racket was as fierce as ever. It was centered now between two gangs — Nick Baroni’s and Sam Dwyer’s river-front mobsters. And now Baroni was on the edge of Dwyer’s territory.

Abruptly the Agent’s eyes shifted and his body grew tense.

The murderous hophead had made his appearance. He was clad in a black jacket, a wing collar, and bow tie. The man was a waiter in this sinister club, a member of the late night shift. Secret Agent “X” was deeply struck by this.

As an employee here, the man was in a position to get orders from any one of a dozen underworld czars — but he was hovering around Nick Baroni’s table. He stepped forward once, struck a match when Baroni skinned the cellophane off a fresh cigar.

Baroni paid no attention to him; but that meant nothing. There were hundreds of prearranged signals by which secret messages and orders could be conveyed.

The Agent watched lynx-eyed. But hours passed and nothing happened. Nick Baroni drank until his face got bloated and mottled. The guests left one by one. Baroni made his exit at last followed by his sinister bodyguards. Secret Agent “X” hung around outside until the hophead emerged again. He shadowed the man to a small furnished room two blocks away.

Then Agent “X” bought all editions of the early morning papers and took them to one of his hideouts. In secrecy and silence he read all available news reports. The story of the murders in Colonel Crandal’s home was spread glaringly in headlines across the front pages. The police had made no headway. The famous Crandal jewels were gone. Three detectives and an old family servant had been killed strangely, horribly strangled apparently by unseen hands. There had, the paper said, been another murder outside the Hotel Sherwood. A man named Greenford, suspected of being an international spy, had met death in the same mysterious way.

Through it all a trail of black mystery ran. The police and Government operatives were baffled. There seemed to be no connection between the jewel robbery in Crandal’s home, the murder of Greenford, and the four other murders of like nature that had taken place previously.

But the Agent’s eyes were grimly alight. He saw a sinister motive, a connection running through it all. But the picture was not clear. Why had the Black Master, who asked a million dollars for the thing he had stolen from the chemist, Mark Roemer, stooped to such a crime as the theft of Crandal’s jewels? Was it merely to provide funds for himself until the big sale went through? Wouldn’t even the Black Master find it difficult to dispose of such famous gems as Crandal’s? And now that Greenford had been murdered, what would be the Black Master’s next move? What government would he attempt to negotiate with next?

These were the questions the Agent asked himself as dawn made the sky gray over the city. Milk wagons rattled in the streets outside. Men and women rose to another day of work. The black mouths of the subways became gorged with hurrying people. But the Agent, silent and alone, pondered a murder riddle.

There was one course open to him, one he planned to follow. He would haunt the Mephistopheles Club, watch developments there, shadow Nick Baroni.

WHEN night came, he was among the first arrivals. Disguised as a young man about town, he played heavily at the gambling tables to avert suspicion. He began to win. Here was more money that would go into Betty Dale’s fund for crime victims.

But he ceased playing when ten o’clock came and when he saw the gross form of Nick Baroni entering the room.

For a moment the big gangster, puffing on a cigar, swept the gambling tables with cold, alert eyes. Then, while his bodyguards moved quietly into chairs around him, he settled himself before one of the roulette wheels. He began playing with the elaborate, solemn concentration of a man to whom gambling is a serious business.

Tonight, Baroni had more torpedoes with him than usual. There were six of the sleekly dressed, vicious-looking young men. With cigarettes dangling from their bloodless lips, their eyes were ever alert. It seemed that their right hands were never far from their right coat pockets, where flat automatics rested. There was a tenseness about them as though they expected trouble. Had Sam Dwyer, terror of the river front, made some veiled threat, warned Baroni that this was his territory?

The tenseness increased when, toward midnight, Baroni left the gambling room and seated himself at a dinner table. The Secret Agent saw why. He saw Baroni’s sloe-black eyes shift across the room. Saw his face muscles stiffen.

There, seated at a table near the wall, was Sam Dwyer, Baroni’s hated rival. The river-front gangster was a thinner, younger man. There was a mocking light in his eyes as he looked across the room at Baroni.

Spatted, immaculately dressed, with the corner of a white handkerchief thrusting from his upper coat pocket, Dwyer looked like a fashion plate. But there was a hard, lean wolfishness about him that matched the older man’s pudgy viciousness.

Ostentatiously Dwyer rose from his seat and walked across the room. Elaborately he bowed to Baroni and gripped his fat white hand. The two men smiled, stared at each other, and hatred glared from their eyes. Baroni’s bodyguards edged nearer, their chalky faces glowing like pale, evil moons against the shadows of the room, their hands tensing like talons. Dwyer’s crafty eyes flashed toward them. He smiled again. The Agent couldn’t hear what was being said, but he knew that Dwyer was giving vent to some mocking pleasantry. The two men seemed like old friends. It was only the bitter lights in their eyes that revealed the murderous enmity they bore each other. The room grew silent, tense.

But Dwyer walked quietly back to his table. He appeared to have no bodyguards around him. He appeared to have come to the Mephistopheles Club alone; but, while he had been talking to Baroni, the tables around the entranceway had filled. Well-dressed, quiet-moving young men, singly and in groups, had entered.

They paid no attention to Dwyer, or he to them. But when Nick Baroni saw the newcomers, a pastiness crept over his fat face. The Agent, watching hawklike, saw the pudgy fingers holding the cigar begin to tremble.

Smiling slightly, Sam Dwyer was studying his menu. The waiters scurrying about the room looked suddenly like small scared rabbits. Whispers ran among them and among the guests. There were covert glances. Frightened gestures. The manager of the Mephistopheles Club walked jerkily across the floor and went up to Dwyer’s table. His face was pale. He remonstrated with the gangster.

Dwyer waved him airily away.

Many guests, still in the middle of their meals, began to rise and hastily leave. Girls, the color suddenly gone from their faces, asked their escorts to take them out. The room was slowly emptying, as the stalking shadows of murder crept out from the walls.

The orchestra on its stand played on, but the music took on a thin, sickly quality. The eyes of the musicians darted from their printed notes to the two groups of men facing each other. Their hands trembled on the keys of their instruments. The rhythm became broken, macabre, like a dance of death.

Baroni was slumped in his seat now. He was trying not to show the fear that made his features dough colored — trying not to let on that he was aware of the showdown that faced him. The stubs of two cigarettes spiraled smoke in the ash tray before him. He lit another and dribbled smoke through his heavy lips and nostrils. The whites of his eyes had taken on a yellow tinge as they wandered toward those tables across the room. He and his bodyguards were outnumbered. Dwyer’s friends had come in strength of two to one.

The Agent’s gaze was upon Dwyer. What would the signal be that would let hell loose in this room?

The sleek, bland face of Sam Dwyer gave no hint But, as the Agent watched, Dwyer’s well-manicured fingers lifted slowly and touched the handkerchief in his front coat pocket. He took it out, wiped his lips delicately. When he replaced it, he thrust it down out of sight.

It was a slight gesture, almost insignificant; but it was the prearranged gesture that started the fireworks. It was the fuse that lighted the bomb of human hate and ferocity.

In one and the same moment, the men around him left their tables and backed against the wall, drawn guns suddenly appeared in their hands. Dwyer slipped out of his seat as quickly and gracefully as a dancer executing a pirouette. With a hoarse bellow of fear, Nick Baroni lurched sidewise in his chair, deliberately flinging himself flat on the floor. He did it to escape the stream of bullets that lashed the spot where his body had been.

Chapter XIV

THE Agent had witnessed many gun fights, but never one which began with such deadly sudden ferocity as this. Both sides were shooting to kill, shooting to achieve the greatest slaughter in the shortest space of time.

Baroni had escaped the first blast of bullets. His huge body was half hidden by the table which he had overturned. It was all that saved him. His bodyguards were crouching, their eyes black, evil slits. Like Dwyer’s men, guns had appeared miraculously in their hands. They answered the fusillade from across the room with a volley that sent a wave of sound blasting back against the walls.

The musicians left their stand, stumbling off it amid a jumble of hastily dropped instruments. They scurried out of sight. The few remaining guests outside of the members of the two gangs, leaped to safety. Only Agent “X” remained as witness of the crimson carnage that was taking place.

He sat at a table close against the wall. There was a heavy portière near by. He drew it in front of him.

The fighting men paid him no heed; but he knew that he risked a stray bullet any moment.

One of Dwyer’s men had fallen to the polished floor of the club. He pressed a hand to his side, screamed, thinly, horribly. A gunman in the employ of Baroni suddenly threw up his hands and took three staggering steps forward. There was a blue hole in the center of his forehead, a surprised look on his evil face. Even before his body hit the floor, there came the vicious splat of three more bullets striking him. He crumpled up and lay still, a crimson stain slowly spreading outward.

Dwyer, a gun in his hand, and the look of a demon on his face, was edging forward. He shouted some orders to his men. They spread out, slinking along the walls, creeping closer to the group who faced them. Dwyer himself crouched behind a chair. His gun spat.

Another Baroni man dropped to the floor. Lying with one arm twisted under him, he kept up a murderous fire, until his automatic clicked emptily. Then, painfully, slowly, he began filling the clip from his pocket until a second bullet shattered his wrist. He screamed then and crawled away toward the wall.

Baroni was getting the worst of it. There was no question about that. This was a battle to the death. Dwyer was fighting to wipe out a rival group, to eliminate competition with the quick scalpel of hot lead. And Baroni’s small bodyguard was already reduced by two.

Slowly, mercilessly, Dwyer’s men moved in fanshaped formation, trying to reach a point where their crossfire would do the most damage. Baroni, his eyes bulging, his face sagging with fright, still lay on the floor. Either the big gangster carried no gun or he was afraid to draw it. He was depending on his men, waiting for death, palsied with terror.

A third Baroni man dropped his gun now. His arm hung limply. He tried to pick the gun up with his left hand, failed. There were only three of them left, crouching, white-faced youths whose lives had been spent under the shadow of fear and quick death. They were fighting with the desperation of cornered animals, knowing that their minutes were numbered.

“Get Baroni,” Dwyer hissed. “The yellow-bellied punk is hiding behind that table.”

Agent “X” saw the mobsters’ fire shift, saw splinters begin to fly from the table behind which Baroni crouched like a sodden, frightened hog.

Then quietly, deftly, the Agent moved his hands. He took a small tool from his pocket — a pair of pliers. They were not ordinary pliers. There was a trough in the middle of them for wires to slip into, a needle point centering in this trough. He snapped the pliers over the cord of the electric table light. His wrist tensed. The needle point was driven through the rubberized insulation, through the strands of copper wire beneath. It formed an instantaneous short circuit. There was a brilliant spark, a puff of smoke. The lights went out as every fuse in the building blew.

The Agent slipped out of his seat. Risking death from the leaden hail of bullets, he crossed the floor, slipped to the side of Baroni. He touched the man’s arm, heard him cry out in fear.

“Keep quiet,” the Agent hissed. “I put the lights out. I can save you.”

He had a reason for this. He felt no friendship, no sympathy for the craven gang lord who had, in his day, ordered the deaths of many men. But there was a chance that Baroni could lead him where he wanted to go — along the trail of the Black Master.

Dwyer’s men, taking advantage of the blackness, were circling in like sinister wolves in the night. A bullet plucked at the sleeve of the Agent’s coat close to the shoulder.

Then someone, a member of Dwyer’s gang, clicked on a flash light, setting it on a chair and leaping back. Its rays illumined one of Baroni’s decimated bodyguards. A volley of bullets riddled him, made him collapse like a slumped sack of grain, before he struck. Only two were left now.

THE Agent smiled grimly. Dwyer’s men were all around them. Guarding the exits, guarding the windows. Dwyer planned to wipe Baroni and every man of his gang out, leave no witnesses of the terrible battle. He would kill the Agent, too, if he got the chance.

But Agent “X” was busy. From a deep inner pocket, he took a small vial with a screw cap. It seemed a strange thing to bring out at such a time, a strange thing to pit against a dozen flaming automatics. In the vial were a score of tiny pellets, like pills.

He unscrewed the top of the vial with deft, quick fingers, then waited a moment while air seeped in. There had been only a vacuum in the vial before. It had been airtight.

On contact with the air the tiny pellets began to smoke and glow.

Suddenly the Agent made a sweeping motion with his arm. The pellets left the mouth of the vial, scattering around the room, rattling on the floor.

A second later one made a report like a giant firecracker exploding. It seemed fantastic that such force could be contained in such a small body. A second exploded close to one of Dwyer’s men. The man screamed with fear, dropped his automatic, and leaped back.

The firing ceased abruptly. Dwyer cursed and screamed orders.

Then a half-dozen of the Agent’s harmless-looking pellets let go, and the room became a crashing, exploding medley of sound. Air waves hurtled this way and that. The windows rattled.

The Agent, calm through it all, spoke sharply in Baroni’s ear.

“They are harmless — come with me.”

The fat gang leader, shaking with terror, floundered to his feet. He stood dazed, rocking, while the din of the exploding pellets kept up.

Leaving his side a moment, the Agent went to the nearest of his henchmen who was still alive.

“Come,” he said.

The man turned with the squeal of a rat, tried to shoot; but the Agent knocked the gun from his hand.

“Fool!” he hissed.

He rounded up the other man, drew them to Baroni’s side. The gang leader gave a brief explanation.

“This guy did it,” he said. “Let’s scram.”

They slunk out of the room, passed an exit from which Dwyer’s men had fled in terror as one of the Agent’s pellets burst close to it. They crept down the stairs unmolested, and out into the street.

An excited crowd was gathering outside. Baroni lumbered through it, scattering people right and left like a hippo ploughing through reeds. His two henchmen and the Agent trailed him.

Down the block two big limousines stood, the fenders of one touching the rear of the other. Baroni piled into the first car. One of his surviving torpedoes took the wheel. Baroni, the other gunman, and the Secret Agent were in the rear. “X” was sticking close to the gangster now, calmly carrying out a preconceived plan.

Gears whined and the car sped away into the darkness. Behind them, police sirens were screaming as a half-dozen radio cruisers, summoned by the frantic appeals from headquarters, converged on the Mephistopheles Club. No doubt the emergency squad cars would be called out, too. It was the biggest gangster battle of the season.

Nick Baroni, slumped and speechless, was mopping his fat face with a silk handkerchief. Rhythmically, monotonously, his plump hands moved round and round. It seemed to afford him relief. His gunman, shivering and crouched like a frightened rat, said nothing as the car tore ahead. But once his eyes shifted strangely, fearfully, to the face of the Secret Agent.

The Agent’s features were the bland, even features of a young clubman. His immaculate tuxedo was not even creased. He fingered his tie for a moment, straightened it. Only his burning eyes showed the dynamic fire of hidden emotions.

NICK BARONI spoke then as the speeding limousine carried them to safety, carried them beyond the noise and turmoil of the Mephistopheles Club.

“What’s your name, guy — an’ what made you chisel in?”

The Agent spoke quickly. This was a question he had been expecting. He was ready for it.

“You seemed to be getting a tough break — and I felt like a little excitement.”

The crafty eyes of Nick Baroni, regaining some of their arrogant poise now, focused on him thoughtfully, taking in his patent leather shoes, his sharply creased trousers, his well-fitted coat.

“Just a playboy out for a little fun, eh!” he said.

The Agent stiffened. Irritation leaped into his eyes for a moment.

“Did I act like a playboy?” he asked harshly.

Baroni seemed to wilt. He opened his mouth, spoke quickly. There was a sudden uneasy look in his eyes, as though he sensed for the first time the uncanny power of the stranger beside him.

“Don’t get me wrong, mister. You came in at the right time. It’s O.K. by me. Those Dwyer rats might have made it a little tough for me. And that popcorn of yours? What the hell was it? How did you think it up?”

“Just a few fireworks,” said the Agent quietly. He had slipped back into his role, hiding his dislike for the man beside him, hiding his contempt for the man’s arrogance and callousness. For Baroni was pretending now that he would have won the fight with Dwyer anyway. He was ignoring the fact that four of his bodyguard lay dead on the floor of the Mephistopheles Club.

“I’ll get that rat, Dwyer,” Baroni was breathing. “I’ll burn his guts for this.” He turned fiercely on the man beside him.

“What do I pay you lice for? Why did you let him get the drop on us?”

“You’re talking through your hat, boss,” said the gunman sullenly. “Burnie, Monk, Steve, and Fred were wiped out. The rest of us would have got it too, if this mug hadn’t edged in.”

Baroni lapsed into silence, mopping his fat face again.

“I gotta have a drink,” he said presently. “My nerves are shot. Stop at Frenchy’s place, Al.”

The torpedo driving the car nodded. A block farther on, brakes squealed and the big car slid to a halt before the door of an underworld dive.

“Come in, guy, and I’ll set you up a snifter,” said Baroni expansively.

The Agent followed the trio to the door of this joint that was still a speak-easy, even though prohibition had been repealed. A slit-eyed man with spiky mustaches opened the door, stared at them through the grating, and admitted them when he recognized Baroni.

“Where’s the rest of the boys?” he asked.

“They got into a little trouble, Frenchy. Fix up some Scotch.”

Darting an inquisitive look at the Secret Agent, the little Frenchman went off to obey orders. Baroni motioned toward a back room and heaved himself into a chair. He was still perspiring. His hands were trembling. His pasty, soggy face showed evidences of the terror that had almost paralyzed him. He gulped three glasses of whisky before turning to the Agent.

“Now,” he said. “What’s your name and who the hell are you?”

“James Porter,” said the Agent quickly. It was one of his many aliases. He drew a card from his wallet, handed it to Baroni to prove it.

The big gangster stared at the card impressed.

“What do you do for a living?”

“Dabble in the stock market a little.”

Baroni’s eyes showed cunning.

“You ain’t making much money now?”

“No,” said the Agent. “You know what happened to the market.”

Baroni rested his fat chin on one hand, placed his elbow on the table.

“Listen,” he said. “You seem like a good guy. Maybe I could give you a job that would bring in some kale. Then you could hit the high places regular. Four of my torpedoes were wiped out tonight. I gotta get some more. How would you like to be one of them?”

The Agent nodded slowly.

“I’ll think it over,” he said. This was what he wanted. This would give him a chance to see what, if any, were Baroni’s connections with the hideous strangler murders. But he didn’t want to appear too anxious.

Baroni took another drink and his self-confidence and suavity increased.

“I got Dwyer’s number,” he said. “I’m going to get him and take over his rackets. There may not be as much dough as when we was running alky — but there’ll be plenty. There’s a dope racket that I’m gonna look in on. You could contact the rich guys and high-steppin’ dames with that million-dollar manner of yours. We could clean up.”

Baroni stared blandly at the Secret Agent, seeming to see in him possibilities for a new type of clean-up — dope peddled to society people who could pay for it. The Agent hid the contempt he felt.

He was about to answer when the three men beside him stiffened. A police siren had suddenly sounded in the street outside. It was followed by the sound of a car sliding to the curb.

Baroni’s eyes darted to the windows in the rear of the room. But a thunderous knocking came at the outside door before he could move. Frenchy, trembling, went to the door. They heard him arguing for seconds. Gruff voices sounded outside. Then the Frenchman slid the bolts and stepped back, wringing his hands.

The Agent, looking over the shoulder of Nick Baroni, saw the foremost figure in the group that was entering. It was Inspector John Burks of the city homicide squad.

Chapter XV

WITH a deep scowl on his face, Inspector Burks strode into the speak-easy’s back room. He eyed the group sitting at the table distastefully.

“Well, Baroni, I figured I’d find you here,” he said.

The big gangster spread his fat hands and shrugged.

“There ain’t no law against a guy having a little drink with a few pals.”

Slowly, sternly, Inspector Burks eyed the faces of the assembled group. He removed his hat, ran quick, tense fingers through his snow-white hair. His contrasting jet-black eyebrows drew together as he frowned.

“Haven’t I got enough trouble with the strangler killings without you gangster rats making more?”

“I don’t get you, chief,” said Baroni blandly. “Me and these mugs have been here all evening.”

“Don’t lie to me,” cried Burks. “Four of your men were picked up on the floor of the Mephistopheles Club — stiffs all of them. You and Dwyer have been fighting again.”

“Maybe we did have a little scrap,” said Baroni. “But I ain’t admitting it.”

“I’ve got fifty witnesses,” said Burks. “You were seen there.”

Baroni’s voice grew unctuous, smooth as syrup.

“Who started it, chief — did anybody tell you that? If I was there and if I fought, it was only in self-defense. The law says a guy’s got a right to—”

Burks silenced him with a wave of his hand.

“Murder is murder, Baroni. Three of Dwyer’s rats were killed, too. You were mixed up in murder tonight. It may land you in the pen, or maybe the hot seat. You’d better come clean.”

A sickly, pasty hue had come over Baroni’s face again. His tone grew whining.

“Listen, chief — maybe I did get mixed up in a little trouble tonight. Maybe there was some guys wiped out. But I didn’t start it, I tell you. It was that rat Dwyer. He’ll get a bellyful of lead for this. He’ll—”

Inspector Burks struck the table with his clenched fist until the whisky glasses leaped and the bottle tipped over, gurgling its amber fluid on the floor.

“I’m going to have a talk with Dwyer, too,” he shouted. “I’m going to tell him the same thing. You two mugs are going to make peace, or I’ll see that you both go to the hot seat. Prohibition’s over. This racket stuff’s got to stop. Both of you are going to break up your gangs and go out of business. If you don’t, I’ll get you on murder charges for what happened tonight.”

It was a threat. The Secret Agent knew that. Inspector Burks was taking what seemed the wisest course. There were few convictions for gang killings. It was hard to get witnesses who would testify in court, harder still to pin crimes on the mobsters. They hired the cunningest, most unscrupulous criminal lawyers to be had. Baroni could plead self-defense. He might get off. But by threatening him, Inspector Burks hoped to win his point.

Baroni’s face muscles sagged. He had visions of a golden stream from new rackets being diverted from his pockets.

“I’ll — I’ll think about it,” he said.

“You’ll do as I say. You’ll bury the hatchet with Dwyer — shake hands with him and go out of business. If I find you in any public place again with torpedoes around you — if there is one more killing, I’ll railroad you both to the pen on a first-degree murder charge. I’m going to talk to the D.A. about it.”

With this ultimatum, Burks turned on his heel and stalked out of the place.

Baroni wiped his face again.

“Let’s have another round of drinks, boys,” he said.

For minutes he sat brooding, his head sunk into the rolls of fat around his neck. He was lost in thought. Finally he spoke.

“You heard what the inspector said. There’s one way of putting it over on that bird. I hate to do it. Maybe I won’t. But it’s worth considering. If me and Dwyer went in together, stopped fighting, we could clean up on dope. Booze is out; but dope’s still good. Now that mugs can get all the liquor they want, they won’t want it so much. We’ll start ’em on dope and get ’em to like it.”

Baroni stopped, took another gulp of liquor. His piglike eyes were gleaming. His shrewdly acquisitive brain was active. He had forgotten the fight in the Mephistopheles Club. Forgotten the dead men on the floor. Forgotten his hatred of Dwyer. Gold took precedence over everything.

“Dwyer and I can open up a swell joint somewhere,” he said. “Together we can keep any other guy from chiseling in. If anybody wants snow or coke they’ll have to come to us.”

The Secret Agent rose.

“Where are you going?” Baroni snapped.

“Out,” said the Agent. “I’ve got some business to attend to.”

Baroni eyed him speculatively for a moment. Then he spoke slowly.

“What I said goes,” he remarked. “I can use a guy like you in more ways than one. You got class and brains. If I hitch in with Dwyer, there’ll be a place for you. Drop around here and Frenchy will tell you where to find me.”

“O.K.,” said the Agent. There was a mocking light in the depths of his eyes that Baroni didn’t get. He was satisfied with the way things were going. If Baroni and Dwyer joined forces, he would have a chance to learn the intimate secrets of both gang chiefs. As a side issue, he’d smash their evil dope racket. But he’d find out first whether either was the Black Master. Now that he thought of it, Dwyer, with his polished manners and suavity, was more the type who might plan such a colossal crime.

BUT, as he stepped into the street outside of Frenchy’s place, the Agent’s calmness left him. He tensed suddenly, whirled toward the curb. His momentary let-up of vigilance had brought new danger upon him.

A dark sedan with lights out was sliding to the curb beside him. The door was open. A voice addressed him from the interior.

“Come here, guy. Stick your hands up.”

The Agent knew the threat of death when he faced it. There was death in that voice. He could see no features; but, just inside the door where the glow of the street light fell on it, he saw the dull, gleaming muzzle of an automatic. He hesitated an instant only, then moved forward.

By the curb he came to a standstill.

“Closer,” said the deadly voice inside.

The Agent moved closer still, his scalp prickling.

Then rough hands seized him. He was dragged into the car’s interior. Almost instantly gears whined and the car shot away. There were three men in the rear of the car. He caught the silhouette of one and held his breath. He was staring at the sharp, wolfish features of Sam Dwyer, river-front mobster, the man who had butchered four of Baroni’s bodyguards.

He did not speak. The car sped on for six blocks. The men beside him were silent; but the hard, cold muzzle of an automatic pressed against his side.

Then the voice of Dwyer sounded again.

“You’re the guy,” he said, “who cribbed our show tonight. I’d have got that hog Baroni if it hadn’t been for those firecrackers of yours. You pulled a fast one — but one of my mugs saw you going out.”

Still the Agent was silent.

“What have you got to say about it?” snarled Dwyer. “Who are you, and since when did you start working for Baroni?”

“Just now,” said the Agent. “My name’s Porter.”

“What do you mean — just now? You helped him make a get-away when I had him trapped.”

“I horned in just for fun,” said the Agent casually.

“Yeah?”

“Yes.”

Dwyer was silent for seconds. He turned on a small flash light, studied the Secret Agent’s face. There was contempt in his voice when he spoke again.

“Just a dolled-up softy,” he said. He swore under his breath and continued. “You shouldn’t have done it, fella. Nick Baroni wasn’t worth it. He gave you a job, you say?”

“Yeah.”

Sam Dwyer laughed thinly, making a sound in his nose that was like a harsh whinny.

“I’m going to save you a lot of trouble, fella. You wouldn’t like to work for Baroni. He’d work you hard. He’s a bad man. You’d come to a lot of grief. I’m going to save you all that. I’m a good guy.”

Dwyer stopped speaking. He laughed again, and one of the others in the car with him laughed, too. Their laughter was harsh, mirthless; it was laughter that held a terrible threat. When Dwyer spoke again, he didn’t address the Agent. He spoke gruffly to the driver of the car.

“There’s a field at the end of Marigold Avenue,” he said. “They’re going to build on it when they get around to it. There ain’t nothing there now. That will be a good place.”

There was coldness, cruelty, in his tone. The driver nodded understandingly and stepped on the gas.

The Secret Agent stiffened. He knew to what use Dwyer planned to put the vacant lot. He knew that they were taking him on a ride of death for the part he had played in Nick Baroni’s get-away.

Chapter XVI

THE pressure of the gun against his side increased. The Agent thought quickly. He had often been in the presence of death. It held no terrors for him. But death before his work was done was something he could not face calmly. The gangster killings he had witnessed had been evil, vicious. But they were as nothing compared to the horror of the Spectral Strangler murders. In his mind’s eye he saw again the swollen, purple face of Bill Scanlon — the tongue thrust grotesquely between lips silenced forever. He saw, too, the features of those others who had met death in the same terrible fashion.

His own face was calm, but his eyes burned with the deep, glowing light of determination.

Sam Dwyer spoke then, harshly, mockingly.

“Baroni can save the dough he was going to give you. You won’t need it; but he will — for funeral expenses. A big shot’s got to have a decent funeral — an’ Baroni comes next — after you.”

Dwyer’s hard, glittering gaze was fixed upon the Agent. The others were staring at him also. There was sadistic cruelty in these men that made them contemplate murder with fierce pleasure.

“Shall we give it to him now, chief, an’ chuck him out afterwards — or wait till we get there?”

The man who had spoken was fingering the cold butt of his automatic. He spoke again, his voice eager.

“It won’t make no noise if I put the muzzle close. The rat cheated us tonight. Let’s smoke him.”

Dwyer answered harshly.

“Pipe down, mug! You’re not giving orders — you’re taking ’em. There’s cops around. We’re not taking any chances — tonight.”

The car rolled on, nearing Marigold Avenue. The Agent knew that it was a long, bleak thoroughfare lined with warehouses and factory buildings. There would be no cops there.

Dwyer corroborated this.

“I’ll give the word when we turn the corner,” he said.

The Agent began to tremble as though in a palsy of fear. They did not know that the man they had captured was a superb actor. The quivering of his arms and body seemed real.

Dwyer’s lips curled back from his white teeth in a mirthless grin.

“Can’t take it — can you?” he said. “Don’t worry, fella — it won’t be long now.”

The others chuckled evilly. Then the Agent spoke, his voice hoarse, as though terror were constricting his vocal cords.

“How about a smoke?” he asked.

“Wait a minute!” Dwyer’s hands felt through the Agent’s pockets for a gun. He found none.

“O.K.,” he said, “but make it snappy. You ain’t got long. The parking ground for rats who don’t mind their own business is just ahead.”

With hands that shook, the Agent reached toward his vest pocket. He seemed to be fumbling, but his fingers were working purposefully. He drew out a silver cigarette case such as a playboy might carry. He thrust a cigarette between his lips, replacing the case, and drew a small lighter from another pocket.

In the dimness of the car’s interior, the gangsters watched his trembling, awkward movements with wolfish satisfaction.

“Soft,” said Dwyer. “You never could have taken what Baroni would have handed you. Better thank us for rubbing you out.”

Dwyer’s gun poked against the Agent’s ribs accentuating the remark. Dwyer laughed harshly.

The Agent was silent. With his left hand he snapped open the cap of the lighter. His thumb was on the tiny knurled wheel that made the flint spark. His right hand hung listlessly in his lap.

Then, so quickly that the men beside him could not catch the movements, he whirled the lighter in a swift arc and clamped the fingers of his right hand over Dwyer’s gun wrist, pushing the gun away.

No spark came from the lighter. There was a soft, quick hiss. A jet of concentrated tear gas, stored in the base of the lighter under pressure, lashed into the gangsters’ eyes.

The man at the Agent’s left clawed at his face. Dwyer at his right cursed furiously and pumped the trigger of his automatic. But the gun, deflected, sent bullets into the back of the front seat.

The driver turned a tense, frightened face. A second jet of gas caught him straight in the eyes. He bellowed with fear, took his hands off the wheel, instinctively jamming down on the brakes.

Agent “X” rose, leaped across Dwyer, and thrust open the car’s door. It was slowing down, wabbling. The front tire struck the curb. The car rocked and slewed around. Agent “X” leaped out, landing on his hands and knees. In an instant he was up, speeding into the darkness, with Dwyer and his men still cursing and clawing at their eyes.

The Secret Agent’s own eyes were glowing. He hoped to get back to the Mephistopheles Club in time to locate the hophead and see what his reaction to the gangster fight had been.

BUT while Agent “X” was still a block away from the club, the hophead was leaving it. He had witnessed the mobsters’ battle, but his small animallike face showed no expression. The police had questioned him among other employees. He had answered in adroit monosyllables, telling nothing. And now he was on his way to his sinister employer.

In killing Greenford, he had carried out instructions to the letter — the instructions of a man he had never seen and probably never would see — the Black Master, the man who supplied him with the soul-shattering morphine derivative that his nerves and body craved. His nerves were jumping now, crying out for a fresh shot of the drug.

The hophead had a report to make to his employer also. He feared no pursuit tonight. Greenford was out of the way. No one else, he felt certain, suspected him of being implicated with the Black Master. Nevertheless, he was careful. The Black Master was a man who tolerated no errors, no oversights. Fear of his unseen employer helped, besides his craving for the drug, to make the man a faithful employee. There was in his heart a dread that amounted almost to superstition for the criminal for whom he worked.

He changed cabs twice, walked along dark, unfrequented streets. On one of them he came at last to a small empty office building. Like the house on Bradley Square, this building was for sale. The neighborhood had run down. It was no longer a business section. The few remaining tenants in the building had been evicted six months before for non-payment of rent. It stood bleak and deserted now, with the chill emptiness peculiar to office buildings that are no longer in use.

The hophead, with a key from his ring, let himself into the front of it. He climbed an old metal stairway to the second floor. Here he entered an office in the center of the building. He touched a switch, turning on overhead lights.

The office was hardly more than a cubbyhole, windowless and airless. The lights he had switched on could not be seen from the street. But, unlike the rest of the building, this office had been renovated. Small as it was, there were indications that someone had recently been at work here.

The place had been dusted, the ceiling and walls had been painted and the light fixtures were new. A huge mirror was set into the rear wall divided in two by a narrow metal panel that ran down its center. The mirror gleamed brightly, reflecting the glow of the lights and sending the dope fiend’s own image back to him. There seemed to be two thin-faced, rat-eyed men in the strange little room.

He studied himself for seconds in the mirror, then glanced at the small clock that was clicking on the table. This was a business office; but mysterious and sinister was the business transacted in it.

The clock showed one minute to twelve. The hophead fingered his collar, tried to control his twitching nerves. There were shadows of fear in his eyes. He waited tensely while the hands of the clock moved slowly round to midnight. Once his gaze darted upward to the elaborate, rose-petal design overhead into which the light fixture was set. Then he stiffened.

A voice suddenly spoke to him out of the quiet of the room.

“What have you to report, Taub? Speak and I will hear.”

The voice was dry, disguised. It was the voice of the Black Master. It seemed to come from overhead, perhaps from a speaker concealed somewhere around the light fixture. It continued:

“I am watching you, Taub. I see your face plainly. Tell the truth — about everything. Don’t lie to me. Never lie to the Black Master. It is not well. He sees all — knows all.”

The dope fiend’s face turned a shade paler. His lips moved. He spoke excitedly — in English that had a slight accent.

“Taub never lies, master. Taub always tells the truth. Taub is a loyal servant.”

A chuckle filled the room. The dope fiend, Taub, began his report, telling in jerky sentences of how he had caught Greenford trying to shadow him and had killed the spy according to instructions. He mentioned, too, the gangster fight in the Mephistopheles Club.

SILENCE had descended as though the very walls were listening. Taub could feel eyes upon him, but he could not locate the direction from which they came. This, too, filled him with dread. He repeated again and again that he always told the truth. The eyes that he felt upon him were real enough. He was under close, continuous observation by a man watching not ten feet away.

In another small office behind the mirror, which formed a heavy partition, the unseen watcher sat. He was facing the mirror, the back of it. Through its surface, which appeared silvered to the hophead, he could see Taub plainly. The mirror was of Argus glass, the glass used in diamond brokerage offices, the glass that will admit light rays in one direction only. It was eight inches thick — thick enough even to withstand bullets. It formed an invulnerable barrier between the rear office and the mysterious room where Taub stood. But, as an added precaution, the man sitting behind it wore a heavy black mask. His features were hidden. Only his eyes showed, watching the dope fiend. Before him was a tiny microphone connected with the amplifier above Taub’s head. He could speak softly into it and his voice would resound in the next room.

When Taub had finished his reports, the Black Master spoke again.

“Greenford was a fool. I do not need him. I have other plans. To make men realize the value of the thing I have to sell, perhaps I shall have to demonstrate it — in a spectacular way.”

The Black Master was silent for a moment. Taub waited. Then the Black Master’s laughter sounded again. It had the harshness of infinite evil.

“You say these two gangs battled — tried to wipe each other out? What if I aided them in their mutual ambitions? What if I gave the police, the city, and the country a demonstration of wholesale killing that they will remember? Nine murders have taken place already. Would it not be more conclusive to the powers that be if I demonstrated what I can do by wiping out wholesale a nest of rats — two nests of them?”

“Yes, master,” said Taub in a trembling whisper.

“I shall destroy Baroni and Dwyer and all those who follow them, Taub. It will be amusing as well as beneficial. As men spray powder on annoying insects and kill them, I shall destroy these criminal parasites. Then — certain men will understand. Then I will get the price I ask for what I have to sell. If not — there will be other murders — till I have made my point clear. You shall aid me, Taub.”

“Yes, master. When do these gangsters die?”

The Black Master was silent for a moment. Behind the mask his eyes glittered.

“When conditions are right,” he said. “When they least expect it. Go back to the Mephistopheles Club, Taub. Find out Baroni’s and Dwyer’s plans. Find out what effect the battle tonight will have. Find out where they can be located.”

“I will, master.”

Taub hesitated after he had spoken. He seemed to be waiting for something — something that he was afraid to mention. The Black Master’s laugh rang out.

“I know what you want, Taub! The laborer is worthy of his hire! As long as you are a faithful laborer, you shall be paid. Come close to the panel between the mirrors.”

Taub moved forward uneasily. He waited in front of the panel. A section of it disappeared suddenly, disclosing a round dark hole six inches in diameter — large enough for a man’s hand to come through. Fingers appeared in this hole, gloved fingers holding a small vial — the fingers of the Black Master.

Taub took the vial. His face was convulsed with the craving that possessed him. Here in this super-potent drug, an opium alkaloid that he could get nowhere else, was peace for his jumping, screaming nerves. It would produce visions that would wipe out the memory of murders he had committed, give him a few hours of rest — and steel him for other murders to come. The Black Master held him in bonds that were stronger than steel chains. He was one of several drug addicts who served the arch criminal. They were safe employees. They would not squeal. To do so would mean an end to their drug supply — with consequent torture to mind and body that would make death welcome.

The Black Master’s hand withdrew. The metal plug inside the panel was shoved forward again. The hole was blocked up. The Black Master’s voice sounded.

“Go now, Taub. Do as I have ordered. Report here tomorrow night. Baroni and Dwyer and their mobsters shall be destroyed like insects — when the time is ripe. Their deaths shall be a further warning that the power of the Black Master is invincible.”

Chapter XVII

TWO days after his escape from Sam Dwyer’s death car, Secret Agent “X” received an invitation. It was handed to him by Frenchy, the owner of the speak-easy where Baroni had taken refuge following the battle in the Mephistopheles Club.

The invitation was from Baroni himself. Secret Agent “X,” disguised again as James Porter, young man about town, had gone to Frenchy’s place seeking news of Baroni. Was there a chance, he wondered, that the two gangsters, Baroni and Dwyer, would forget their animosity and join forces in a new and more sinister racket, as Baroni had proposed?

It seemed possible. The greed for gold was the motive that made gangs organize in the first place. It was stronger than hate — stronger even than the fear of death. And if these two men organized, Secret Agent “X” wanted to watch them. One or the other might conceivably be the terrible Black Master. Or, in contact with them, he might be led to the hideout of this greater criminal.

Baroni’s message was short and to the point.

“Porter,” it said, “come to my place at eight this evening and come dolled up. Big doings, and I can use guys like you. Frenchy will tell you where to come.”

Agent “X” read the note with interest. What was Nick Baroni planning? He spoke to Frenchy, and the rat-eyed, spike-mustached proprietor of the speak-easy gave him Baroni’s address. It was in a flashy suburb built up with the gaudy mansions of the newly rich.

Prepared for any emergency, Secret Agent “X” went there at the appointed hour. He had “dolled up” as Baroni had suggested. He was dressed immaculately, dressed in the height of fashion. No one could guess, looking at him, that in the linings of his tuxedo were many small, curious articles that would have no place on the person of the playboy that he seemed to be.

Baroni, as “X” had suspected, lived in one of the most elaborate houses in that pretentious section of the city. It was ornate with bay windows, towers, and colonial columns. A long drive led up to it. Well-clipped shrubbery covered the lawn.

A manservant who had the sneaky look of a gangster admitted him.

The inside of the house was even more ornately elaborate than its exterior. Here the ex-beer-runner indulged his childish impulses and showed his shockingly bad taste. Pictures, art objects, tapestries, and indiscriminate pieces of furniture formed a confusing jumble. Thousands that he had made in illicit enterprises had been spent in decorating this house.

The air was heavy with cigar smoke. There came the clink of glasses from a room opening off the front hall. The squint-eyed servant ushered Agent “X” into this.

Baroni’s thick voice boomed out. Surrounded by a group of his underworld followers, gunmen, fences, paid torpedoes, the gang leader was in his glory. Arrayed again in an ill-fitting dress suit, he welcomed Secret Agent “X” boisterously.

“Here’s the guy that I was telling you about,” he said. “Here’s the guy that’s gonna throw in with us — him an’ his firecrackers.”

He was introduced to the circle of men whose bland faces masked depths of evil. The two surviving torpedoes of the night before were there. Four new ones had re-enforced them. In such hard times there were few crooks who were not glad to join in with Nick Baroni. The gangster looked at his watch.

“We’re gonna start in ten minutes,” he said.

“Start where?” asked the Agent.

Nick Baroni winked at him, broadly, mysteriously.

“I got a little surprise for lots of you guys,” he said.

The hired torpedoes hitched the guns in their pockets expectantly, thinking apparently that another battle was in store. Baroni turned on them suddenly. His face was serious now. He waved his cigar in pudgy fingers.

“None o’ that,” he said. “You mugs are going to leave your rods behind tonight. They won’t be needed.”

Astounded looks met this announcement. Baroni nodded.

“Yeah, I mean it. Get un-heeled before you leave. If any guy has a gat when he steps out of this house, I’ll have him put on the spot.”

Glumly the men about him rose and deposited their automatics on a sideboard in the big room, making the sideboard look like a young arsenal.

“How about you, fella?” said Baroni, staring at the Agent. “Ain’t you heeled?”

The Agent shook his head.

“I’m not carrying a gun,” he said.

Baroni looked sly.

“Don’t set off any of them firecrackers, either. You got to act polite where we’re going.”

Mysteriously he rose then and beckoned for the others to follow.

THEY put on their coats and hats, and, when they reached the porch outside, a collection of limousines awaited them. Some were Baroni’s own cars. Others he had hired for the occasion. Their drivers seemed to know where they were going. No directions were given. The Secret Agent had a place of honor in the first car with Baroni. The fat gangster, full of zest tonight, joked and laughed as the cars rolled away.

They headed back toward the city, drove in a procession through the night streets. Then the Secret Agent gave a start of surprise. The cars were drawing up before a familiar entranceway — the door of the Mephistopheles Club. Hadn’t Baroni had his fill of bloodshed and violence in this place?

As nonchalantly as though no killings had ever taken place there, as though there had never been bleeding, bullet-riddled corpses on the floor, Baroni entered. His followers came behind him, gaping, wondering.

The club’s manager came out to meet them. A few whispered words and he led Baroni across the main floor. They climbed a short flight of stairs, entered the club’s biggest private dining room. Then the Secret Agent started again.

A huge table was set in the center of the room. Gleaming plates and silverware showed. Spotless napery spread like a field of snow under the lights. At the table, ranged around it, waiting, was a group of men. But it was the man at the table’s head that caught the Agent’s eye.

Sam Dwyer!

A sudden tenseness filled the room. Baroni’s torpedoes crouched in their tracks, their hands stiffening, forgetting that they had left their rods behind. Baroni waved a sudden affable hand. He spoke suavely.

“This is the surprise I was talking about. Me and Sam here has buried the hatchet. We’re gonna behave ourselves now. There ain’t gonna be no more killings. All you mugs has gotta make friends and get acquainted. Ain’t that right, Sam?”

The thin, dudish gangster at the head of the table rose.

“Business before pleasure,” he said. “Maybe Nick Baroni and I would like to sling a little lead at each other, but it don’t pay. Times have changed, boys. Nick and I are going into business together. This is a dinner to celebrate our partnership. We both know our stuff. We oughta make good.”

Dwyer’s eyes focused on Secret Agent “X” for a moment. Sudden malice sprang into them.

“That guy!” he said. “You brought him along, too, Nick?”

“Why not?” said Baroni. “What if he did pull a little stunt here the other night? We gotta forget all that.”

“I wasn’t talking about that,” said Dwyer. “It’s something else. I don’t like him.”

As though in bitter recollection, the thin gang leader rubbed his eyes for a moment. They were still slightly bloodshot from the traces of tear gas that Secret Agent “X” had flung.

“Whadda yer mean?” asked Baroni.

“Nothing,” said Dwyer. “But keep him away from me.”

“He’s gonna sit at my end of the table,” said Baroni. “But you fellas has got to be friends, too. Everything’s gotta be peaceful from now on. We both gave Inspector Burks our word.”

Baroni winked again leeringly. The two gangsters were keeping their word to the head of the homicide squad. They had buried the hatchet, made up with each other. But “X” knew what sinister ambitions filled the breasts of the two men. They hoped to flood the city with narcotics, fatten like vultures on the broken bodies and broken souls of drug addicts.

The men of Baroni’s gang eased into their places. Waiters came in. Suddenly Secret Agent “X’s” eyes grew intent. Among them he saw the slim, cat-footed form of the dope fiend he had shadowed, the emissary of the Black Master.

The hophead had evidently been detailed by the club manager to wait on the gangster’s tables. The rat-eyed man looked around for a second, then disappeared to return a moment later.

In his arms this time he carried a huge floral piece. There was something funereal about it. Roses, carnations, and cornflowers were wired in a big frame. More wire was wrapped around the thick bundle that their stems formed. Maidenhair fern formed a mat around this. But, funereal as it was, it made a gay display.

Baroni and Dwyer turned their heads in surprise.

“For the gentlemen,” the hophead waiter said politely.

“Who’s it from?” barked Baroni.

The waiter shook his head.

“Bring it here — let’s look for a card,” Baroni demanded.

The waiter picked the flowers up, brought them close. Baroni looked amid the gay blossoms, shook his head.

“There ain’t no card,” he said. “It’s from the manager of this joint — or maybe the police commissioner himself. Set it down over there, you pasty-faced mug.”

The waiter nodded and drew the mass of flowers into a position where all could see them.

“They make me think of a funeral,” said Baroni. “But they smell good. Bring on the food and let’s eat.”

SECRET AGENT “X,” watching the face of the waiter, had a sudden, tingling sense of danger that he couldn’t quite fathom. But there was a look in the hophead’s eyes that was hard to interpret — a look of uneasiness, of expectancy.

It was the hophead who helped serve the soup course, and “X,” missing nothing, saw that the man’s hands were shaking. Something was wrong with him. Something was in the air. What?

The courses of the dinner progressed. The gangsters ate their food, drank their liquor, and grew noisy. Baroni hurled jokes across the table at his former enemy, Dwyer. The hands of a clock at the end of the room moved toward ten. As the hour approached, Agent “X” noted that the hophead’s manner grew more mysterious.

A dusty whiteness had come over the man’s already pale face. His small eyes rolled in his head. Twice they stabbed across the room, focusing on the clock. He almost spilled the coffee in serving it.

At five minutes to ten, with the huge meal over, Nick Baroni rose to his feet and proposed a toast.

“To the future of this gang,” he said. “To all the dough we’re gonna make an’ the good times we’re gonna have.”

They drank gustily, emptying their glasses. Baroni ordered another round and spoke again.

“This has been a swell meal,” he said. “I want the guys who cooked it and the guys who served it to come in and drink with us. I want the club manager, too.”

The hands of the clock stood at two minutes to ten now. The Agent’s eyes were focused not on Baroni but on the rattish, evil features of the hophead waiter. He saw the man’s gaze move toward the clock for the dozenth time; then the fellow slipped furtively toward the door. His movements were quick, scared at the last. He seemed to want to get out of the room as though it harbored some terrible evil — something that struck dread to his soul. Baroni saw the man’s movements.

“Here,” he said: “You gotta drink a toast, too, you dope-eating mug.”

The waiter shook his head and jerked open the door.

“Get him — bring him back,” roared Baroni. “Just for that I’m gonna pour whisky down his throat till he can’t stand up. He ain’t no gentleman.”

Secret Agent “X” leaped up. More than any one else in this room he was interested in the waiter. What could account for the man’s strange actions? He did not want him to get away. He flung out the door after the man, saw him darting down the hall. The hophead was running as though all the devils in hell were after him, running as though to escape death itself.

Agent “X” pursued him as far as the end of the corridor. Then a sound made him turn his head and look back. The door that he had just left, the door of the dining room, had swung open. A man stood in it, a man clawing at his throat.

The man was one of Baroni’s henchmen. As the Agent stared in horror, the gangster’s eyes bulged, his face grew purple, and, with a hoarse, terrible cry he pitched forward and lay writhing. Another figure followed him, a man who seemed to be fighting invisible terrible fingers encircling his neck.

As he held the door open for a moment, Secret Agent “X” got a look into the room he had just left.

A gasp of sheer horror came from his lips. For the room was a shambles. Men at the tables had risen to their feet. Chairs were being overturned by reeling, staggering figures. Purple faces showed.

Then suddenly the bark of an automatic sounded. It was followed by another and another. Some of the mobsters who had come to the dinner “unheeled” had worn concealed weapons. They were using them now. Each gang held the other responsible for the thing that was happening. Leaden death slugs were being added to the horror of invisible murder.

Two men, clawing fiercely, fighting like demons, lurched through the door. One was a Baroni man; the other a henchman of Dwyer. Tho latter held an automatic. The Baroni man was pinioning his wrist. But the man with the gun jerked free as a sinister purple hue spread over his enemy’s face. Before the unseen strangling death could do its work, he sent three bullets crashing into the head of the Baroni mobster.

Then he dropped his gun, clawed at his own throat. In a few seconds he had collapsed to the floor to join the body of the man he had just killed.

Sam Dwyer himself came from the dining room. His immaculate clothes were in disorder now. His sleek hair was streaking down his face. He wrenched at his freshly starched collar as though that were the thing that was cutting his wind off. Then he gave a fearful scream and staggered against the wall. The livid, plum-colored hue of the strangling death spread over his face. His eyes started from their sockets, and he fell forward on the floor.

It was like a glimpse into the mouth of some ghastly inferno. Agent “X” shuddered. The Black Master had struck his most hideously ironic blow.

Chapter XVIII

NEWSBOYS were shouting in the streets three hours later. They were peddling papers on which were spread headlines telling of the greatest underworld killing in the city’s history. Tense-faced men and women were reading the story. The police were staggered by the magnitude of the crime. The Baroni and Dwy-er gangs had been wiped out. The two gang leaders and all their followers but one, dining in state at the Mephistopheles Club, celebrating the end of their long feud, had been slain. Two score men had been killed by the horrible strangling death.

Cordons of police still surrounded the Mephistopheles Club. Grim-faced detectives were viewing the scene of this most colossal of crimes.

It was the one surviving member of the gangsters’ party that aroused the press and the police to a state of hysterical excitement. Employees of the Mephistopheles Club remembered having seen him coming from the corridor of the private dining room. He had left the building just before the terrible crime had been discovered. The manager of the club had seen him, too. He gave a description to the police.

“Tall, well dressed, even featured — a typical playboy.” This was what the manager had said. He remembered having seen this man in the Club Mephistopheles before. He had been there two nights previous when the gangs of Baroni and Dwyer had had their bitter battle. No one knew his name. But dozens of detectives were detailed to comb all the underworld of the city. Descriptions of the man were sent out to every precinct. Every patrolman on the beat was on the watch for him.

Inspector Burks of the homicide squad, called to the scene of wholesale murder, believed that he had seen the man also. He had his own opinion as to the man’s identity. He remembered that it was at Frenchy’s speak-easy on the night he had warned Baroni not to battle with Dwyer, that he had seen the mysterious stranger.

Detectives were sent to question Frenchy. Trembling and white-faced, Frenchy babbled the truth. The playboy stranger was not a regular member of Baroni’s gang. He had helped Baroni in some way. Baroni had invited him to the fatal party. Frenchy had overheard Baroni and the stranger talking. The stranger’s name was James Porter.

Armed with this information, the police increased their efforts. They even searched the membership lists of the exclusive clubs. Newspapers gave the man’s name to their readers with the request that any reader who heard of him, telephone police headquarters immediately.

But no call came in. No one had heard of James Porter. The name was obviously an alias.

Inspector Burks, hearing this, swore fiercely. The police commissioner of the city was beside him at the moment. The Inspector turned to him, spoke with the bitterness of a man who is baffled and distraught.

“James Porter and Secret Agent ‘X’ are one and the same,” he said. “Secret Agent ‘X’ is the man behind all these crimes. He’s the murderer we want to get. I said so that night at Crandal’s home. I say so again now. This city will have no peace until he is behind bars waiting for the electric chair.”

The police commissioner nodded gravely, convinced that Burks was right.

And, sitting tensely in a restaurant in an entirely different disguise, Secret Agent “X” was studying the papers. There had been no time to make an investigation of the death room in the Mephistopheles Club. He had his own ideas about how the mass murders had been committed. He remembered that floral piece which had been presented to the gangsters with no name attached. The Black Master’s drug-crazed slave had brought it in. The Black Master was behind those terrible deaths. But, in his horror at seeing the shambles in the room, Agent “X” had lost sight of the hophead who had disappeared.

HE knew at whom the hunt was being directed. Toward the man who called himself James Porter — toward himself. There was irony in that. He was fighting the Black Master, risking his life. So far he had come nearer to the truth than any one else; but the police were convinced that he was the murderer. The papers were calling him the Black Master.

From the description that Frenchy of the speak-easy had given, several staff artists on several newspapers had drawn pictures of the disguise Agent “X” had worn.

These were being run on the front pages of the paper as an aid in identifying him. He realized by what miracle he had escaped death in that room. But his own alert faculties were partly responsible; these and the fact that he had been suspicious of the hophead.

A floral offering! “Like a funeral,” Nick Baroni had said, and the mass of gay flowers had masked a death more hideous than any one in the room had suspected. Why had the waiter kept looking at the clock? Why had he left like a frightened rat as the hands approached ten? The answer came forcibly to the Secret Agent’s astute mind.

At the hour of ten, the Black Master had sent out the waves of radio impulse which had operated some hidden engine of death concealed in that mass of sweet-smelling flowers. The brain of a master criminal had conceived of the terrible plan.

Agent “X” was waiting, reading the papers, wondering when the police would examine the floral offering. But even if they did, he hadn’t any hope that it would lead them in the right direction. The Black Master was too clever a man to leave clews that would point the way. The police might guess, as he did, how the murder had been committed, but they wouldn’t be any nearer knowing who the murderer was.

As the Agent read the stories of the crime, studying, pondering, a special delivery letter was received at the city headquarters of the U.S. Department of Justice.

It was a letter that brought the chief of the office, working late, out of his chair. A letter that made him strike the desk with a clenched fist. It was a letter from the Black Master.

There at the bottom of the page in typewritten capitals the arch murderer’s name was printed. There was nothing phony about it. The contents of the letter showed that it was genuine.

“Gentlemen:” the letter said. “At this moment you are reading newspaper stories and listening to police reports of the murders that have taken place at the Mephistopheles Club. Look at the mailing date on this letter. It was dropped in a post office box at ten o’clock. That was the hour that the murders took place.

“The writer of this letter has a weapon of such terrible strength that the Government cannot afford not to buy it. The Government has seen now what it can do. It has seen men stricken down at a precise hour in a terrible way. I am offering this weapon for sale. It is now on the market. Several countries are interested in it.

“My price is high. But if my price is not paid, other atrocities will follow. I destroyed a nest of rats tonight. The Government, I know, will thank me for this. But, if my price is not paid, a reign of terror will follow in which people who are not rats will die. If that is not sufficient evidence that I mean business, I will move my base of operations to the nation’s capital.

“Think well over this. Consult with your superiors. My theft of the Crandal jewels will give me sufficient funds to carry on. I am prepared to wage an indefinite campaign until my demands are met. If some other country buys my weapon first, that will be America’s loss.”

The Department of Justice official read this letter again and again. He called his colleagues to his side. The city police heads were shown the letter. Messages flashed back and forth between them and Washington. But if the Black Master meant what he said, if he were not a madman, it was a baffling, terrible problem. No civilized country would consider the use of such a terrible weapon even in the chemical warfare branch of its army. The Black Master must be caught, destroyed, before his terrible campaign had reached shocking heights.

A day went by, and no progress was made. That evening, in his office, a public official received a threat. It was from the Black Master telling him that he had been marked for death.

He called up police headquarters. Squads of detectives and Government operatives were sent to guard him. A cordon was thrown around his home to see that no stranger entered. Motorcycle cops rode beside him as he left his office in his own private sedan. The chauffeur was an old and trusted employee. But a detective rode beside him.

When the official reached the safety of his home, he was prepared to stay under cover for days if necessary — for days till the Black Master had been caught. The block was cleared as the official’s car rolled up to his house. Detectives watched from all sides.

Then, just before the car stopped, just before the door was opened, the official and the two men with him were seen to rise and clutch at their necks. As detectives rushed forward, they lurched from the car with purpling, hideous faces, clawing at their throats. They staggered, reeled, and fell dead on the sidewalk with their tongues protruding in the mocking, characteristic manner of the strangling death.

A hasty search of the car’s interior revealed only one thing. The tiny electric bulb in its roof was broken. Bits of glass lay on the floor. The mystery of the Spectral Strangler was as black as ever.

Chapter XIX

AGENT “X” read about this murder in the papers. That night he called on Betty Dale. It was late. She had just returned from the Herald office. Her eyes were wide with fright and excitement.

“I was afraid,” she said. “Afraid something had happened to you.”

The Secret Agent nodded.

“The hounds are chasing a fox while a wolf runs free.”

“The Black Master,” she said. “Do you know that he made a broadcast to the papers tonight? Do you know he threatened a campaign of terror if the Government does not meet his price?”

The Agent shook his head.

“You wouldn’t have heard about it,” said Betty Dale. “The broadcast came just before I left the office. It was on a special short wave. They haven’t been able to trace it.”

“They won’t,” said the Agent harshly.

She saw by the burning, intense look in his eyes how deeply the news affected him.

“The whole city is hysterical over it,” she continued. “Rewards are being offered for the Black Master’s capture. My paper has offered ten thousand dollars. Colonel Crandal has offered another ten. The loss of his jewels — those murders at his home — have shaken him. He came to the office tonight. I talked to him. The police commissioner came, too. They all think it’s you. If I could only tell them that it isn’t!”

“Let the hounds of the law chase the fox,” he said bitterly. “The fox will hunt the wolf.”

Again fear sprang into her eyes.

“I am terrified,” she said. “Terrified for you. He — the Black Master — seems able to strike anywhere. And you were there at the Mephistopheles Club when those awful murders took place, when all those gangsters were killed!”

He nodded and for a moment patted her hand. There was a light in his eyes warmer than the burning glow of the man-hunter. He was human for a moment, glad that somewhere in all the world there was one person who knew he was not a murderer, glad of the friendship and abiding loyalty of this sweet girl.

And the flood of color suffused Betty Dale’s cheeks again. The Agent’s fingers upon hers made her heart beat strangely. She wanted for an instant to have him put his arms around her, to melt into them and beg him for her sake not to risk his life. But this would be interfering, hindering the strange, important work to which he had dedicated his life. She spoke primly, almost casually, checking the flood of words that sought to pour from her lips.

“Be careful,” she said. “Don’t take any chances you don’t have to.”

Secret Agent “X” left her with grim determination in his heart. Three times now he had moved in the wrong direction. Each time, however, he had drawn nearer his goal; yet each time the Black Master had won the point, while Death kept score. The man, whoever he might be, was a monster of cunning as well as cruelty. He was holding the whole detective force of the city at bay, fooling them utterly. And now he had even dared broadcast to the papers, telling them of the campaign of terror he planned.

The Agent knew that the Black Master had a dual purpose in this. It was a free advertisement of the hideous thing he was trying to sell. He was letting the whole world know that the murder weapon he used was on the open market. He hoped by such means to start competitive bidding, to raise its price.

And this made the Secret Agent think of Piere DuBrong and the blonde woman, Nina Rocazy. What were they doing?

He made many discreet inquiries. Countess Rocazy had been staying at the Hotel Imperial for a few days. But she had checked out. It was believed she had gone South. Piere DuBrong had left for Washington. But a long-distance call to the embassy office elicited the fact that he was not expected back for several days.

A grim light showed in Agent “X’s” eyes.

He changed his disguise, got one of the cars he kept out of a garage, and silently drove through the night. In the mid-town section, he parked his car and walked along a quiet street. Then he stopped in front of a small apartment building.

This was the place to which he had escorted the blonde after their memorable ride in the speeding taxi.

Was she still here? Was this her hideout when she wasn’t playing the role of countess?

HE looked in the mail boxes. The name of Rocazy was not there. Perhaps she had another name, or perhaps she had moved again, gone quietly to some hideout where she could consort with her own kind. He did not believe for an instant that she had left the city.

The Agent remembered the location of her apartment. He stared up the side of the building. A fire escape moved past a window in one of the rooms she had had. The window was dark, curtainless. The apartment seemed empty.

But the Agent moved along the side of the building and drew himself up on the fire escape. Muscles hidden under his well-tailored clothes worked with springlike quickness and precision. Noiselessly he climbed upward till he was on a level with the third-floor suite Nina had had.

His observation from the street below had been correct. Nina’s apartment was empty. Not only that. Plasterers had been at work getting the place ready for a new tenant. Small drops of splashed calcimine showed on the inside of the window.

Pressing his face close to the glass, he could see the workmen’s stepladders, pails, and brushes standing in the middle of the room. All the furniture had been moved out.

It seemed futile to search for traces of Nina’s whereabouts inside. But the Agent hesitated only a moment. His quick mind was working. He never overlooked small bets. He remembered a thing which he had noticed in his one quick survey of the place. The room had an open fireplace. An ordinary detective would have passed this by. But Secret Agent “X” tried to pass nothing by.

He drew his kit of chromium tools from his pocket, thrust the clawlike teeth of one under the window sash. The place was empty. He could risk a little noise now to gain entrance quickly. If there was nothing here, he did not want to waste time.

He pressed down on a rod-like handle which he fitted into the tool. The sudden, tremendous leverage snapped the lock. In a moment he was inside, walking on quick, silent feet. There might be someone in the apartment below. Overhead footsteps would attract attention.

Painters’ canvasses, spread over the parquet flooring, helped to deaden the sound. He drew out his tiny flash light, turned its beam on the fireplace. Then he moved forward eagerly. An old broom leaned against the bricks of the fireplace. The painters had carefully swept the floor before starting work.

He had noticed that Nina hadn’t been a neat housekeeper. A woman in her dangerous line of work had no time to think of the little domestic niceties. There was a miniature mountain of gray dust and gray ashes on the cold hearth of the fireplace.

The Agent had studied the habits of all types of people — careful people, slipshod people.

Crouching before the fireplace with his small light turned on, he began raking through the ashes and dust with a splinter of wood that the painters had used for mixing plaster.

He worked slowly, painstakingly, missing nothing that the fireplace contained. When he stopped at last, he held three objects in the palm of his hand — the stubs of two cigarettes with lipstick adhering to them, and the crumpled cardboard covering of a package of matches. He discarded the cigarette butts after a close examination of them. They had no name, but a sniff convinced him that they had been Russian.

His eyes glowed when he stared at the match paper. “Café Levant” it said. A border of gold stars and scimitars on a blue background framed the words. The Agent turned back to the ashes and raked again. He unearthed several bits of charred cardboard. These, too, were blue.

He had conclusive proof now that the woman, Nina, made a habit of going to the Café Levant. She bought her matches and cigarettes there. She flung her stubs and empty match papers in the fireplace. All this fitted in with his estimation of her character. She was exotic, slipshod. She might have changed her living quarters, but, if she were in the city, he doubted if she had changed her eating place.

Agent “X” left the apartment quickly and stopped at the nearest telephone. But the Café Levant was not listed. Grimly, purposefully, he called up the service department of the city’s lighting company. He was a workman, he said, sent out on a job. Where was the Levant Café located? The girl on duty looked in her books, gave him the address.

The place was far downtown, near the water front. The entrance to it was shadowed by the elevated which snaked overhead like an endless black serpent. There were small cluttered shops of Syrian, Armenian, and Arabian pastries along the street. Agent “X” smiled. If she made a practice of coming all this distance to dine, she would undoubtedly keep it up.

The Agent, looking like a sight-seer who had casually wandered in, entered the grimy doorway of the Café Levant.

It was nothing more than a small, smoky restaurant serving Russian and Oriental foods. The large, greasy proprietor stood behind the cashier’s desk near the door. There were a dozen people in the room, sitting at the small, soiled tables, and Agent “X” noticed one thing immediately.

The buzz of conversation ceased as he entered. This was a place where the same diners came night after night. It was a place unadvertized, unknown to the world uptown. The coming of a stranger was noticed at once.

But the Agent sat down casually at a table near the door.

He did not at first return the glances that were directed his way. Conversation began to rise again after a time. It seemed to him that it came in a medley of many different tongues.

His gaze swept the mixed men and women diners, and he saw then that their faces like their voices showed the blood of many countries. The Café Levant was the meeting place of at least a dozen different nationalities — the meeting place perhaps of international spies. And suddenly he bent down, staring at the menu card, hiding the glow of excitement that filled his eyes. For, sitting at a far corner table, talking to a shabbily dressed man, was the woman he sought, the blonde spy, Nina Rocazy.

Chapter XX

FROWNING at the bill of fare as though its exotic dishes were unfamiliar to him, the Agent finally signaled the hovering waiter. He ordered coffee and pastry.

Over the steaming cup of thick Turkish mocha, he furtively scrutinized each face in the room. However shabby their clothing might be, the people around him had a sharpness, an intelligence that seemed out of keeping in this smoky little place. There was a tenseness in their manner, an avid look in their eyes.

He had suddenly the impression that the room was filled with human vultures, quarreling, distrustful, hovering near some prize piece of carrion.

The blonde, Nina, did not glance his way, or, if she did, saw nothing to make her gaze linger. She looked older, more strained. The man with her was as tense and bright-eyed as a hunting hawk. They fitted in with the general atmosphere of this room. It was as though the murders of the past few days had whetted their appetite to possess the Black Master’s secret weapon, as the sight of raw meat whets the appetites of a group of tigers. The heads of Nina and the man were close together.

What was she telling him, “X” wondered? Was she attempting to blackmail him also, as she had Greenford? Apparently not, for the man’s face had the intentness, the greed, of someone who expects gain.

Agent “X” finished his light meal and left the Café Levant, walking swiftly away. At the end of the block, staring back over his shoulder, he saw the greasy-skinned proprietor come out onto the sidewalk and stare after him.

Agent “X” circled quickly, walked around the block and approached the café from the other direction on the opposite side of the street. There were little shops here, closed up for the night, their windows dark. He backed into the entranceway of one, fumbled a moment with one of his master keys, and opened the door softly.

In the dark interior he crouched, waiting. Looking through the dusty window at a slant he could see the door of the Café Levant. Those coming out of it would never see him, never suspect that they were being spied upon. He could take no chances now. Too many lives hung in the balance.

If the Black Master was not caught soon, the sinister threat of his presence would grow into a horror that would shock the whole nation. “X” had seen the gangsters wiped out like insects. The thought of innocent people being destroyed in the same way made something clutch at his heart as though icy fingers were pressing there.

There was no question in his mind but that those men and women in the Café Levant were spies, here in America to dicker for the Black Master’s secret. Just as crooks sought each other’s company, so, too, there were places where the undercover operatives of various nations gathered. But these in the Café Levant were, he guessed, for the most part the rabble. Their loyalty could probably be bought by any country willing to pay the price.

Several people entered the Café Levant; several emerged; but it wasn’t until nearly an hour had passed that the blonde Nina made her appearance. The hawk-faced man was with her. He was tall, slightly stooped. He was still talking excitedly, leaning over her. They were absorbed, their faces close together in the darkness. This was no mere amorous intrigue. The softness of love in any form was not upon them. They were like two stalking jungle animals, male and female.

When they had nearly reached the end of the block, the Agent emerged. He closed the door of the shop softly after him, moved along in the shadows under the elevated structure. They took a cab down the block, and the Agent followed in his car.

Blocks away, in a Bohemian section of the city, the cab stopped and they got out. Agent “X” parked and got out also. He followed them again until the trail led to one of a row of small, old-time houses on a crooked little street.

Here artists and writers lived, radicals and long-haired poets. Here, too, apparently, international spies found refuge, for the man opened the door of the house with a key and entered with the blonde at his side.

There were no lights in the old house until Nina or the man pressed a switch. Then a glow appeared in a second-floor room. Apparently they had come here to continue the subject under discussion.

The Agent thought quickly. An impulse stronger than a hunch told him that these two were after the death weapon of the Black Master. Nina herself had informed him that that was her purpose in coming to America. She wasn’t the type of woman to give up easily a thing she coveted.

SILENTLY as a shadow, the Agent sprang up the steps of the old house and unlocked the door with one of his skeleton keys. Then he checked himself and tensed. He had almost made a fatal error. He could pick any modern lock, open any present-day door, but a protective device on the door of this old house had blocked his way.

There was a heavy brass chain inside, bolted to the wall, its end slipped into a slot on the door. He could not reach it with his fingers. He had almost pushed the door against it. To have done so would have meant a rattle that might have warned the two on the floor above.

Many minutes of patient work would be needed to devise a way of unfastening that chain. The lower front windows were shuttered.

Grim-lipped, the Agent moved swiftly along the block and went around to the rear of the house. The rear door, too, was fastened with a chain. There was no fire escape snaking up the back of the old place, no way of getting to the unshuttered windows on the floor above.

But the Agent wasn’t balked. There was still a possible way of learning what those two in the room were discussing. To do so, however, he had to reach the roof of the house they were in.

The houses in the row on the block were all of the same height and period. He walked along till he found another one empty. The old door, with no chain fastened, opened easily under one of the keys he carried. He closed it behind him and swiftly climbed the stairs.

Uncarpeted boarding creaked under his feet. A mouse squeaked and scurried away. There was a smell of dust and mold in the air. It reminded him of his own hideout in the old Montgomery mansion far up the drive.

He reached the attic, found an old iron ladder leading up to a skylight. It was the work of a moment to un-snap the four hooks that held the skylight cover in place. A second more and he was up on the tarred roof, three stories above the street.

Counting the houses as he moved, he crossed swiftly from roof to roof until he was on the building where the two had gone in. Looking cautiously over the coping, he could see the glow of their windows a story below. The shades were closely drawn. From his vantage point he could not look in. The skylight, he knew, was fastened on the inside. The two in the room imagined themselves safe from all listeners. But the Agent drew from his pocket a device which might invade their privacy.

He unfastened a flat, black leather case, took out the delicate mechanism it contained. It was perhaps the smallest telephonic amplifying device in existence — a thing that he had worked patiently on in his spare moments.

A dry battery like that in the smallest flash light gave it power. Wire hardly thicker than thread connected between the single earphone and the amplifying microphone of the instrument. He had fifty feet of the wire strung on a small reel like a spool. This spool was pivoted inside the case itself.

He walked softly to the chimney in the center of the roof, stood on his toes and stared down. It was a two-passage chimney connected with open fireplaces in the front and rear rooms. This he had guessed as soon as he had seen the old house. It had been built in the days when open fireplaces were the only means of heating. There was a faint glow visible far down the sooty throat of the chimney. But it was not the glow of a fire. No smoke or heat was coming up the chimney. It was the glow of the light in the room shining into the fireplace. A gas stove probably supplied heat, and they had not bothered to light a fire.

The Secret Agent held the microphone end of his miniature amplifier in his right hand and slowly lowered it down the chimney. He unreeled the threadlike wire with his left. He dared not drop it all the way. If it appeared in the square opening of the fireplace, it would give warning to those below.

By the length of the wire he had lowered, he estimated the distance. The bell-shaped microphone of his instrument must now be close to the room where the two had gone. It must be hanging just out of sight in the fireplace.

He made a turn of the wire around the chimney to hold it, then stooped and bent over his delicate mechanism. He switched on the small dry battery, the voltage of which had been stepped-up with special chemicals. Two brass screw heads gleamed inside the case. One induced clarity. The other regulated volume.

WITH the receiver of the amplifier clamped to his ear, the Agent crouched in the darkness of the roof and began to listen. At first only a faint blur of sound reached him. He turned the delicate knurled head of the clarifier adjustment. Gradually the blur of sound resolved itself into human voices. But they seemed faint and far away — the voices of pigmies talking in some subterranean cave.

His fingers remained on the clarifier adjustment till the sounds had reached needle sharpness. Then he turned on the volume control.

Like a distant radio station coming into earshot, the voices in the room below grew in size, grew till it seemed that the lips of the people who spoke were close to the Agent’s ear. His tiny-microphone, made with exact scientific skill, was doing its work.

He could even hear the extraneous noises that the two in the room made, the faint stirring of their feet, the creaking of a chair, the noise the man made as he cleared his throat.

It was Nina who was speaking at the moment.

“I am nervous, Gustav — always nervous since Grenfort was killed. I am ready almost to give up — and go back.”

Agent “X” heard the woman’s restless footsteps as she paced. A man’s harsh, jeering laughter sounded.

“That is the way of women — brave until danger comes!”

“But Grenfort—”

“Grenfort was a fool, a bungler. You are talking to Gustav Mogellen now. He does not bungle. Grenfort did something to anger this absurd madman who calls himself the Black Master. We don’t know what. We cannot say. But I have not angered him. I have treated him with deference like the lunatic he is.”

“You are a fool yourself to talk like that, Gustav. The Black Master is not mad. He is a criminal, and he wants money just as you and I do.”

“Bah — all Americans are mad.”

The man chuckled softly, then spoke to the woman again.

“They will have something to be mad about later when they find that a nation was willing to buy what they scorned and feared.”

“You are sure, Gustav? You do not intend to trifle with the Black Master?”

“Trifle! I might, in a gay moment, trifle with you, a charming woman, but I would not trifle with this madman. I tell you Gustav Mogellen is wise. He does not trifle with infants, animals, or madmen. What I have told him is true. My country is willing to meet his absurd price.”

“It seems unbelievable,” gasped Nina.

“Unbelievable! Unbelievable that a small nation like mine should want to possess a weapon that will give it dominance over others! In the event of war—” There was a slap as the man below struck his fist against the palm. A laugh followed the blow. “In the event of war we should win by the sheer horror we would inspire in our enemies. Armies would refuse to fight. Men would throw down their arms. In my two sessions with the crazy monster in that mad office of his, I have convinced him that I am not fooling. I would not dare fool. Each time I have left it, I have been followed, shadowed. One slip, and I would die like our dear friend Grenfort. Tonight I go to make final arrangements. Tomorrow night, to show my good faith. I will give him an advance payment of fifty thousand dollars — a mere option — but he has agreed to cease his sensational activities and wait quietly till the payments are completed. In a few weeks the weapon that all men fear will be ours.”

Chapter XXI

FOR nearly an hour, or until the tiny battery in his amplifier began to give out, the Secret Agent listened. The man, Gustav Mogellen, gloating, triumphant, continued to impress the woman with his astuteness.

Agent “X” wondered if her fear were genuine, if she were not playing some deeper game. He wouldn’t trust her not to murder the man, say that he had been killed, and take whatever commission his government planned to pay.

But that didn’t interest him. It was the immediate future upon which his mind was set. A foreign power was planning to pay the Black Master his price, buy Mark Roemer’s stolen formula. This must not happen! The murderer of Bill Scanlon must not escape.

With tense, quick fingers the Secret Agent reeled in the threadlike wire of his amplifier. Carefully, fondly, he put it away in its case. That tiny instrument was all that had stood tonight between America and a plot that might become a menace of world importance.

His eyes were glowing with that strange, burning light as he left the roof by the way he had come. There was much to be done, a hundred chances that he might slip up.

Far down the block he waited, watching the door of that house where Gustav Mogellen had discussed his plans with the blonde. And it was toward midnight that he saw Mogellen emerge. The man, dressed in a dark overcoat walked quickly into the shadows.

Now as never before Secret Agent “X” used his uncanny skill as a shadower. Mogellen looked around once, saw nothing, and strode on. He seemed confident that no one guessed what affairs he was about.

Agent “X” saw him take a taxi at the junction of the street and a nearby avenue. The Agent followed blocks behind in his own car. His sharp, burning eyes, staring ahead, missed nothing.

When the taxi turned a corner, he sped up. When at last it slowed and stopped, he, too, parked, still blocks behind. But he almost ran through the darkness. He was watching as the man, Mogellen, entered a block of empty office buildings. The onward sweep of the city seemed to have left this section deserted. Business offices had been moved farther uptown. No wonder Mogellen in his talk with the blonde had referred to this place as the Black Master’s “mad office.”

The Agent saw Mogellen look around once, then fit a key into the building’s front door. He saw him disappear inside. Two hundred feet ahead, Agent “X” saw another flitting shadow.

He crouched back in the darkness. The man in front was the hophead, the murderous, vicious employee of the Black Master. He saw the man creep forward into the building after Mogellen. He stayed there, no doubt, close at hand, unseen, ready to kill the visitor if anything went wrong.

For twenty minutes the Agent waited amid the darkest shadows on the opposite side of the street. Then he saw Mogellen emerge and move rapidly off. The small, wicked-looking dope fiend slipped out of the building and followed after. The man, probably, had been instructed to shadow Mogellen all the way home, to kill if his actions became in any way suspicious. But Mogellen did not look back. He walked swiftly on, disappearing down the block.

Agent “X” remained in hiding a half-hour longer, then stole forth and quickly crossed the street. He was at the very gates of death now. But he gauged his time. He must search this building while the hophead was away shadowing Mogellen, and finish his search before the man got back.

Noiselessly he fitted a key into the lock and entered by the door through which the spy, Mogellen, had gone. Did the Black Master live here, or was it only his place of conducting business? The cold, damp chilliness of the unheated building made “X” believe that the latter was the case.

Risking sudden death, not knowing what he might find, he began probing with his tiny flash light. In the dust of the floor he was able to trace Mogellen’s tracks. He followed them, coming at last to the small, strange office on the second floor. The Agent saw instantly that there was only one door into this office.

He flashed his light, then waited breathlessly — waited for possible death. But nothing stirred. In that one flicker of light he had noticed the mirror covering the rear wall, the mirror with its metal panel down the center.

It had meant nothing to the disordered mind of Taub, the dope fiend. To Agent “X” it instantly conveyed meaning.

He had seen such mirrors in the doors of high-class speak-easies in the days of prohibition. From them the proprietors could look out, but no one could see in. The proprietors could tell just who was ringing the bell, customer or prohibition agent.

Just so the Black Master could look through this mirror at any visitors who came into his office. Was he behind it now? The thought that unseen, sinister eyes might be upon him was spine-chilling. But the Agent gambled all on logic. He felt the surface of the mirror. It was as cold as the rest of the room. It seemed unlikely that the Black Master would linger on in this cold, damp place. He had no doubt left at the conclusion of his interview with Mogellen.

Working on this theory, risking all, the Agent boldly switched his flash light on and began examining the mirror. He soon discovered the round crack in the center of the panel and guessed that there was a secret opening here. It clarified many things in his mind. The hophead had probably never seen the face of his employer. No one, conscious of the fact, had ever looked at the features of the Black Master and lived.

Agent “X” tested the opening in the panel. It was, he saw, fastened tightly on the inside.

He went out into the hallway, investigated, and found that in the remodeling of this office the whole second floor plan had been changed. There was no visible entrance to that room behind the mirror. The way by which it was reached might be from almost any direction. There might be a secret stairway leading up or down, passageways leading even through empty buildings into some other street. To hunt for the hidden entrance would be a lengthy process. Worse still, it would scare the Black Master away.

The Agent knew then that the man must be outwitted if he were to be caught at all. Quickly, quietly, he went away from the mysterious office, leaving it exactly as he had found it. A theory was building up in his mind — a theory that had slowly been dawning. To test that theory he began to construct a startling, fantastic plan.

IT was twenty-four hours later, with darkness again spread over the city that Agent “X” climbed for a second time to the roof of the house occupied by the blonde woman, Nina, and Gustav Mogellen.

Lights burned in the windows of the second floor. The hour was ten. Secret Agent “X” carried a leather suitcase in his hand. He knew that the two were again in the room. He had shadowed them there. He was prepared to risk everything on the plan he had devised.

He took a box from his suitcase, opened it, and again lowered something on a wire down the chimney. But this time it was not a microphonic amplifier. This time it was a small metal cylinder capped at both ends.

One of the caps was held in place by a strip of fusible metal. Electric wires were attached to this in such a way that when current passed through the wires the fusible metal would heat up and melt — releasing the cylinder’s cap and the cylinder’s contents.

The Agent lowered it swiftly. At the instant that it appeared in the square opening of the fireplace below — the instant a faint shrill scream told him it had been seen, he touched a switch connected with a small but powerful storage battery in his suitcase. Nothing happened apparently. But the scream was not repeated. No sounds came up the chimney from the room below.

The Secret Agent drew his cylinder back up. He rewound the wire and packed it in his suitcase. Then he took out a strong rope. One end of this he fastened to the base of the chimney. The other he lowered over the rear edge of tile roof and climbed down it agilely.

He was not careful to be quiet now. He knew there was no one to hear him. He jimmied a window on the top floor and climbed in, pulling his suitcase after him.

Down through the house he went to the room below. The lights were still on. The Agent held his breath and threw up a window. Then he waited outside a few moments. When he entered again, the night air had cleared the room of the anesthetizing gas it contained — the gas he had released so quietly from his metal cylinder.

The forms of a man and a woman lay on the floor. One was Nina, the other, Gustav Mogellen. Both were breathing quietly, as though in a deep untroubled sleep. They would remain so for hours.

The Agent deposited the woman on a couch, made her comfortable. She was a killer, a murderess at heart, a plotter of evil; but early training made him always more gallant to women than to men.

Gustav Mogellen he propped up in a chair and tied there with a piece of rope.

A small leather brief case was on a table. The Secret Agent went over, opened it, and examined the interior. The brief case contained fifty thousand dollars in United States currency. It was in bills of large denomination, done up in neat packages. The Secret Agent smiled to himself. Here was the “option” money to be paid to the Black Master tonight. He added a package of tens and one of twenties from his own pocket, then put the money back in the brief case, returned to the side of Mogellen. For long minutes he studied the man from every angle. There was no line of the face, no skin blemish, that he did not take note of. Tonight the Agent’s very life, the lives of perhaps untold others, depended on his skill.

He set to work then on one of the most masterly disguises of his career. With his make-up materials spread on the small table, with his pigments, face plates and volatile plastic materials before him, his dexterous fingers began to accomplish the seemingly impossible.

With clinging, quick-drying face putty, the Agent duplicated Mogellen’s hawklike nose. The planes of his face followed. At the end of half an hour it seemed that two Gustav Mogellens were in that small room. If the blonde Nina could have regained consciousness at that moment, she would have thought the gas that knocked her out had made her see double.

WHEN all was ready, when the Agent had put on the last finishing touches, practiced Mogellen’s walk, imitated the sound of his voice as it had come to him over the amplifier, he took the keys from the spy’s pocket and picked up the brief case.

He crossed the room, shut the window, slipped into Mogellen’s hat and overcoat. Turning out the lights, he descended to the street and locked the door after him. He was going to meet the Black Master tonight for the first time. Even if the Black Master’s dope-crazed slave were watching outside, he would not guess that the man he saw was not Gustav Mogellen.

The Agent traveled swiftly through the night in a hired taxi. He left the cab behind him, walked along a block of silent, empty buildings. Whether the hophead was waiting to follow, to spy on him, he did not know or care. At the moment he was not Agent “X.” He was Gustav Mogellen, international spy, interested in making a down payment on a secret and horrible weapon that was for sale.

He fitted Mogellen’s key into the lock of the deserted building, entered, and closed the door after him. He listened a moment. His sharp ears detected faint movement somewhere in the darkness. The murderous hophead was following close at his heels.

He entered the small strange office on the floor above and turned on the lights. This time as he did so he heard some mechanism in the door click metallically and the lock snapped shut. He was trapped in the room.

He looked at his watch. It showed one minute to midnight. He waited, fingering his tie, registering the uneasiness that a spy might be supposed to feel on such a strange mission.

Then a voice spoke to him out of thin air. A strange, harshly disguised voice that he had heard before. The voice of the Black Master.

“You are on time, Gustav Mogellen. You are anxious to clinch the bargain!”

A second of silence followed, then the Agent answered.

“One does not keep the Black Master waiting,” he said, imitating the voice of the man who now lay unconscious in the house a mile away. “I have the money I promised. I am ready to seal the contract. My government has kept its word.”

A dry chuckle came from overhead.

“Your government has done well. Yours will be a strong nation. Approach the panel between the mirrors. I am ready to accept the money — and remember! You are locked in this room — a prisoner until our negotiations are completed.”

Agent “X,” posing as Mogellen, hesitated a second.

“When,” he said, “can I hope to receive the secret weapon? I shall have to cable my government for details?”

“When the last payment is delivered,” said the Black Master. “The quicker the payments, the sooner the thing that you seek will be given into your hands.”

“And you will remain silent and hidden from now until all payments are completed?”

“Yes. There shall be no more killings. The Black Master will appear to be dead. He will appear only in this room to transact his business with you.”

The Secret Agent nodded. He came close to the panel between the mirrors. A small, six-inch opening in its center appeared as if by magic. The fingers of a hand reached out. They were black-gloved, almost invisible against the blackness of the opening. The Secret Agent thrust a package of his own ten-dollar bills into the hand. The hand withdrew.

“For your own convenience,” the Agent said, “I am making payment in small bank notes. Big bills arouse suspicion and are more easily traced.”

“You are thoughtful,” came the sneering voice of the murderer.

A package of twenties followed the tens. The fingers of the Black Master’s hand seemed to express the inhuman greed that their owner felt. They curled avariciously, reaching for more bills.

Then it was that the Agent’s left hand dipped into his pocket and drew something out. So swiftly that it was like a trick of legerdemain he transferred the object he had removed to the palm of his right hand, slipping a package of bills over it. Under cover of the bills, his finger pressed into it. It was a small thimblelike cap with a sharp needle point at its end.

He passed the package of bills to the eager, black-gloved hand of the arch-murderer. Then, quick as the head of a striking snake, he jabbed the needle on the thimble cap into the Black Master’s hand.

One faint, harsh cry came through the black hole in the panel

The Secret Agent’s hand darted through it — clutched the arm of the man inside, drew it toward him, and turned the beam of a small flash light into the opening that was left.

The light rays fell for a moment on a masked face.

The Agent thrust the mask aside — and gave a harsh exclamation of surprise. For seconds he stared tensely; then he let the inert body of the man inside fall.

As it did so, a signal bell sounded somewhere in the building. To his horror, Agent “X” heard stealthy, quick footsteps answering the bell. He guessed instantly that the hophead he had seen was only one of several vicious degenerates who were slaves of the Black Master.

His scalp prickled as seconds passed. The threat of unseen death stalked through the empty spaces of the dark building. The seconds deepened into minutes — one — two — three. Then suddenly, the lights in the room went out. The Agent was alone in the strange, dark chamber with the knowledge that doom was creeping upon him.

Chapter XXII

HE waited tensely till a faint noise sounded over by one wall. There was a scrape of metal, the mouselike squeak of a hinge. A mysterious panel door was opening. He could not see it, but his sharp ears and tensely alert mind told him what was happening.

Agent “X” moved then. He took three silent strides to the wall, flattened himself against it, and inched toward the spot where the noise had come from. His fingers crept ahead of him, feeling, exploring. They discovered a break in the wall surface, and he paused, as still as death.

He could hear faint breathing now. A man was standing only a few feet away, crouched before the opening that the panel had left.

Secret Agent “X” drew back on his toes. Then, using the flat of his hand and his arm like a battering ram, he gave the unseen man a violent shove. At the same instant, he leaped through the break in the wall. With a jarring, sickening thud he bumped into a human body. In one and the same motion he clutched the man, whirled him around, and threw him headlong. Then his swiftly groping fingers found the panel and drew it shut.

As he did so, something crashed against the closed metal — something that had been thrown at him and missed. The tinkle of breaking glass came; then a horrible gurgling scream sounded. It was a scream of terror, of agony, of stark despair. It was followed by the thud of wavering, stumbling footsteps. Clawing fingers slid down the panel, beat against it, but the Agent held it shut. To open it meant death for himself as well as those others now beyond human aid. For faint, acrid fumes seeped around the edges of the oblong of metal. They were burning to the nostrils, constricting to the throat.

The stumbling footsteps inside grew more disordered. Two bodies thudded to the floor. Then silence — the silence of death — filled the strange dark building.

The Agent waited for minutes more, holding the panel shut, until the seeping fumes had thinned and vanished. Then he opened it cautiously. The air inside was still stuffy but breathable. The last of the fumes slipped out of the room into the passageway in which he stood and passed him like an evil spirit escaping.

He turned his flash light into the chamber. Horror met his eye. Two huddled figures lay on the floor, their faces contorted by the strangling death. But the skins of both and the dilated pupils of their staring eyes indicated that they were drug addicts. The tongues of both were thrust from between blue lips as though mocking him. But the Agent had not killed them.

They had died by the force of the evil thing they dealt in — died by the weapon with which they had tried to snuff out the Agent’s life. Small splinters of glass lay on the floor by the bottom of the panel. They told a hideous story.

The Secret Agent stooped over the body of one of the dope fiends who would murder no more. He felt in the man’s pockets. Wrapped in a nest of cotton was a tiny crystal globe. It might have been a Christmas tree ornament — but it wasn’t. The Agent didn’t need to be told what it contained.

It was a globe of imprisoned gas — corrosive gas so strange and deadly that it had the power to constrict a man’s throat until he choked to death. Gas, however, that would dissipate after a few moments of contact with the hydrogen in the air, losing its power, leaving no trace, its deathly work done. Gas that was Mark Roe-mer’s secret — a horrible weapon which he had discovered during the course of his researches and planned to discard — but which unprincipled governments desired as a weapon of war. It was more efficient than lewisite or mustard gas which left trenches uninhabitable for hours and prevented a conquering army from moving in. It could be used to attack civilian populations, to create a reign of terror worse than long-range guns or air bombs. The Secret Agent shuddered, glad that he had been in time.

HE looked around the room for a moment. The whole story was here. The dead hopheads. The sinister crystal globe. Those glass splinters on the floor — and the unconscious man behind the barrier of mirrors. Who was he? Let the police find out. When they came there would be little to do — except batter through the mirrors and make the most sensational arrest in the city’s history — the arrest of the Black Master.

But there was one question burning in the Secret Agent’s mind. Where was Mark Roemer — kidnapped chemist? He was a witness needed to complete the amazing denouement. The Agent turned his light into the opening of the wall panel again. The mouth of a passage showed.

He entered this, closed the panel after him, and walked forward till he came to a flight of secret iron stairs leading up. He went cautiously. There might be more of the murderous hopheads. He probed with his flash light, listened every few seconds; but he encountered no one. The stairway led him to an attic of the building. Here were three rough bunks, a table, packs of well-thumbed cards, and a smoky oil lamp. Here were the quarters of the Black Master’s slaves. Then he saw a heavy door with a lock upon it at the end of the room. There seemed to be a closet-like room behind it. The lock had been newly placed there. The Agent’s eyes gleamed, and he took out his kit of chromium tools. The lock gave him some trouble, but he finally opened it.

As his flash winked on, it illuminated the thin, haggard face of a middle-aged man. The man had evidently been waked from sleep by the Agent’s work upon the lock.

He was crouched back on a small, rusty bed in this windowless room — crouched fearfully like a frightened animal. He did not cry out, but his bony hands lifted. There was the fear of death in his eyes. His feet were fastened to the foot of the bed by chains and the bed was bolted to the floor.

“Roemer!” said the Agent tensely.

“Who are you?” The man, who had been kidnapped and held a prisoner for days, spoke in a shaken, terrified voice.

“Never mind! Listen to what I say and all will be well!”

The Agent walked forward, his burning eyes commanding the gaze of the kidnapped chemist. A low-voiced conversation followed. At the end of it Secret Agent “X” left the room, descended by a series of iron stairways to the ground floor, and passed quietly out into the street.

Before changing his disguise Agent “X” did two things. He stopped in an all-night drug store and bought a heavy manila envelope and stamps. Into this he put the packs of bills he had taken from the spy Gustav Mogellen. He placed cardboard around the bills, sealed the envelope up carefully and addressed it in disguised writing:

“To Mrs. William Scanlon, care of U. S. Department of Justice, Washington, D.C.”

Once again his lips moved as he whispered that sentence that had rung through his mind like a war cry in his battle with the Black Master.

“A kid and a woman are waiting.”

Fifty thousand dollars wouldn’t compensate for the death of a beloved husband and father. But it would make life easier for a woman who had a young son to bring up.

“I hope he turns out as swell as his old man,” the Agent muttered huskily. Then he turned and moved into a telephone booth.

A HALF-MINUTE later, a mysterious call came into police headquarters. It was a call that brought the sleepy desk sergeant up from his blotter with a jerk. The sergeant tensed as he listened. His hands gripped the telephone like claws.

When the message was ended, the sergeant asked the name of the person who had given it. There was no answer. A low laugh sounded. Then the receiver at the other end clicked up.

The sergeant, red-faced, his eyes bulging with excitement, called Inspector John Burks, head of the homicide squad. He dared even to get Burks out of bed, refusing to listen when Mrs. Burks said her husband had a cold.

“Cold, hell!” said the sergeant. “I got a tip-off. The Black Master’s been caught. Mark Roemer’s been found!”

When the inspector came to the telephone, the tenseness in the sergeant’s voice, and the news that he had, electrified Burks into action.

In ten minutes he was speeding down town in an official car with two police cruisers and a squad of detectives trailing him. He went to the address that the mysterious party who had called the sergeant had given. This was an old and apparently deserted office building on a dark and run-down street.

The next half-hour was one of the most exciting in Burks’s whole career.

What the police found in that building Burks told a group of tense press reporters who had gathered like buzzards, following the wailing sirens of the homicide cars.

Burks was still mopping his face from the intense activity of the past few minutes. He knew that the newspaper men were waiting. He knew that he was the man of the hour. With trembling fingers, he lit a cigar and blew smoke from his nostrils before he spoke. They were standing in the Black Master’s small office. The double mirrors were broken now, smashed in by police axes. Burks waved his hand toward them.

“That gave us the biggest job, boys,” he said. “Those mirrors were eight inches thick.”

A tall red-headed reporter edged forward. No one seemed to know him, but he had a press card. There was a faintly malicious gleam in his eye.

“How was it the man behind those mirrors didn’t scram while you were breaking them down?” he asked.

“Wait — I’m coming to that,” said Burks a little irritably. “First I want you to know that we’ve got the Black Master and Mark Roemer, the man he kidnapped. Roemer has told us his story. He was being held to make the gas he’d invented when the supply on hand ran out. He didn’t want to do it. He would rather have bumped himself off — but Roemer’s got a young daughter in finishing school. The Black Master threatened to kill her if Roemer didn’t do as he was told.”

“And who’s the Black Master?’ shouted the reporters. “Come on, Inspector — don’t hold out on us!”

Burks grinned like a showman about to display a prize exhibit. He waved his hand, gave an order.

“Bring him out, boys!”

TWO perspiring cops came through the jagged opening broken in one of the big mirrors. They carried the limp body of a third man. This man had a black mask over his face. The reporters seethed forward.

“Take it easy,” said Burks. “You got a big surprise coming.”

With a sweep of his hand, he drew the black mask back.

The reporters tensed. One of them swore harshly.

“God! Colonel Gordon Crandal!”

“That’s the boy,” said Burks. “He won’t do any more murdering now. He’s headed for the hot seat or the bug house.”

“It can’t be! It sounds phoney,” said a rosy-cheeked reporter.

“I thought so, too,” answered Burks, “until Roemer spilled all the dope.”

“But Crandal’s own jewels were stolen!”

“I know it. He stole ’em himself to get the insurance. He’d lost all his money in the stock market. He didn’t have a cent left — and he was too proud to work. Too proud, too, to sell his house or the jewels. He wanted to keep on being a gentleman. He had to have a lot of money quick — so he figured out a way of doing it. He was in the chemical warfare division during the Big Fuss. He knew what the stuff that Roemer had, the gas, was worth. He must have been shell-shocked, I guess, to turn into the kind of crook he is.”

“He’s not dead then?”

“No — only knocked out. I wanted to get him alive — make him stand trial.”

The troublesome red-headed reporter asked another question.

“You were pretty clever to knock him out before you broke down the glass!” he said.

Burks glared at the speaker.

“The police have a lot of tricks up their sleeves,” he said.

“And this joint,” went on the reporter, “only a pretty smart bird would have thought of looking here. How did you get wise, chief?”

A slow red spread over Burks’s face.

“I’ve told you guys all I’m going to,” he said.

“One more question, chief,” persisted the redhead. “Didn’t you pass it out a few days back that the bird who committed these murders was a crook named Secret Agent ‘X’?”

“I was working on a bum steer,” said Burks defensively. “But I delivered the goods in the end, didn’t I?”

“All by yourself,” muttered the redheaded reporter innocently. His head was bent. He seemed to be writing on his notebook. When he straightened up, Burks was glaring at him. For the space of five seconds the two men’s eyes clashed. The reporter carelessly dropped a leaf from his notebook and mumbled:

“I’ve got to be getting back to the office.”

He turned and left while Burks stood staring, frowning and puzzled. His footsteps clattered down the stairway, and suddenly from the night outside an eerie yet melodious whistle sounded.

Burks swore and started for the door. But as he did so, his eye fell on the scrap of paper the red-headed reporter had dropped. On its white surface something had been written, a small penciled letter — the letter “X.”

Before any one else could see, biting the end of his cigar nervously, Inspector Burks moved sidewise and planted his foot over it. There he stood, the look of puzzlement in his eyes, while the strange musical whistle in the night outside grew fainter and fainter and finally died away.