Paul Drake, Della Street and Kerry Dutton were gathered in Mason's office the next afternoon. Dutton, still somewhat dazed from the rapid developments of the day, said, "Would you mind telling me how you did all this?"
Mason grinned. "I didn't," he said. "Lieutenant Tragg did. Lieutenant Tragg had to."
"Well, the papers certainly gave Tragg a wonderful spread of publicity. One would have thought he originated the whole idea."
"An officer has to take credit," Mason said. "It's part of the game. When Tragg consented to go with me, he knew I'd give him all the publicity if the scheme paid off-and keep him out of it if it didn't."
"But how did you know what had happened?"
"It was just simple reasoning," Mason said. "So simple that I almost overlooked it.
"Palmer was killed shortly after nine o'clock, but the murderess needed a Patsy, so the murderess picked on you. She decoyed you into going to the scene of the murder because she knew Palmer had been trying to put the bite on you. Just before you arrived, the murderess fired another shot so that if anyone happened to be listening, there would be the sound of a shot that would coincide with the time the murder was supposed to have taken place.
"Then, of course, you very stupidly played into the hands of the murderess just as she had expected you would, because she had planted Desere's gun by the body-a gun which she had taken from the bureau drawer in Desere's bedroom."
"And the reason?" Drake asked.
"Not the reason that any of us had thought of.
"Palmer had been in two hotels when these stocking strangulation murders had taken place. The police had, quite naturally, considered him as a suspect, but very foolishly they didn't consider him as a witness. They didn't ask him in detail about the people he had seen in the hotel although he probably wouldn't have told them if they had asked.
"We know now that he had seen Hedley in each of the hotels, and Hedley was the mysterious person who had registered under an assumed name and then vanished. The description fits him."
"And Mrs. Hedley knew what her son had done?"
"Her son has been a little bit off ever since he was a boy. She has a fierce protective instinct-an instinct which was strong enough to make her willing to kill if she had to in order to protect her boy.
"But the point is Palmer knew what Hedley had done, and Palmer desperately needed money to win his proxy fight in the Steer Ridge Oil Company. He felt that he could ultimately gain a million if he could only get operating capital.
"So Palmer put the bite on Mrs. Hedley. It was blackmail for the highest stakes possible. Either he got money or he put the police on the trail of her son on a series of murders.
"That's always a dangerous gambit. Palmer knew that, but he was playing for big stakes. He had to take the chance.
"And he lost his gamble."
"Hedley, himself, didn't-"
"Hedley, himself, didn't know anything about Palmer's murder," Mason went on. "It was his mother who was trying to protect him; his mother who killed the man who could have betrayed her son.
"When you stop to think of it, it had to be the mother. She could have had access to the bureau drawer in Desere's apartment. She was the only one who could have secured that gun, who had a sufficiently strong motive to commit murder if she had to.
"Hedley really gave himself away during that fight with you, Kerry. He ran into Desere's bedroom. He was looking for a nylon stocking. If he'd got his hands on one you'd have found him an expert garroter. He's had lots of practice.
"It was thinking about that rush to the bedroom and trying to find the reason for it that started me thinking along the right line."
Dutton shook his head. "I can still feel the arms of that metallic chair in the gas chamber."
"You certainly led with your chin," Mason told him, "trying to protect the girl you loved and trying to surprise her with an inheritance.
"Now then, make me a check for five thousand dollars covering my fee and Drake's expenses. Get out of here, hunt up Desere Ellis, tell her you love her and ask her to marry you."
"That last," Dutton said, "is probably the best advice I've ever had."