Lion of the Sun

PART ONE

Captivus (The East, Spring-Summer AD260)

'What is it like to lose one's native land? Is it a grievous loss?'

Euripides, Phoenissae, 387-8

Maximus lay motionless watching the Persians. They were in front of and below him, towards the middle of the small upland meadow where three paths came together. They were not above forty paces away. He could see them clearly: in the pale moonlight, men and horses were solid, dark-grey silhouettes. There were twenty-one Sassanid cavalrymen. Maximus had counted them several times.

The Sassanids were confident. They had dismounted and were talking quietly. They were unavoidably in the way. Maximus raised his eyes to check the position of the sickle-shaped, three-night-old moon. There was not much of the night left. With northern Mesopotamia overrun with Persian patrols, Maximus and the others had to be safe behind the walls of Zeugma by dawn. There was no time to retrace their steps or to cast about for another path which ran east-west through the high country. If the Persians did not move on within half an hour, the Romans would have to try and fight their way through. It did not promise well. They were outnumbered three to one. Demetrius had never been much of a one in a fight, and old Calgacus was wounded. Sure, but it did not promise well at all.

Moving slowly, hardly moving his head a fraction, Maximus looked over at Calgacus. The old Caledonian was lying on his left side, favouring his bandaged right arm. His great domed, balding skull blended well with the white rocks. Maximus was fond of Calgacus. They had been together a long time – nineteen years, since Maximus had been bought in as a slave bodyguard to the familia of Ballista. Of course, Calgacus had been with Ballista since the latter's childhood among the Angles of Germania. Calgacus was a sound man. Maximus was fond of him, although not as fond as he would be of a good hunting dog.

Maximus studied his companion, the dark lines of his wrinkled forehead and the black pools of his sunken cheeks. Truth be told, Maximus was worried. Sure, Calgacus was tough. But he had seemed old nearly twenty years before. Now he was wounded, and the last four days must have taken it out of the old bastard.

Four days earlier, they had watched Ballista ride out from the trapped army, one of the five comites accompanying the emperor Valerian to his ill-fated meeting with the Sassanid King of Kings Shapur. They had done what their patronus Ballista had commanded. As the imperial party rode west, they had crossed the perimeter to the south and doubled back behind the eastern slope of the hill. The small group of horsemen – Maximus, Calgacus and Demetrius, Ballista's Greek secretary, along with eight Dalmatian troopers – had made no great distance north when they were challenged by a Sassanid picket. Maximus, the only one who could speak Persian, had shouted out the password, which Ballista had discovered from Quietus, the traitor who had led the Roman army into the trap: Peroz-Shapur.

The Sassanids were suspicious. They had been told to let through only one party of Roman horsemen heading north and shouting, 'The victory of Shapur', and one had already passed. Yet they drew back, their dark eyes scowling, their hands on their weapons.

Maximus and the others had ridden on. Not too fast, so as not to look as if they were fleeing; not too slowly as to appear to be flaunting themselves. Against every instinct for self-preservation, they kept to a gentle canter.

Behind them, a lone rider, baggy clothes flapping, horse kicking up puffs of dust, had raced across the plain. He spurred up to the Persian picket. There was gesticulating, shouting. The easterners kicked their boots into the flanks of their horses. They gave tongue to a high, ululating cry. The chase was on.

Pushing hard, Maximus and the others had galloped out of the valley of tears. They did not see Valerian, Ballista and the other comites hauled from their mounts and, dusty and bloodied, hustled away into captivity. They had no time to spare a glance for the remainder of the Roman field army of the east, surrounded and hopeless on the hill. They had a large party of Sassanid light cavalry only just over two bowshots behind them. They rode hard to the hills of the north-west.

Darkness had saved them. It seemed an eon coming, then all at once it was there. A dark, dark night; the night before the new moon. Calgacus, whom Ballista had chosen to be in charge, had ordered them to double-back to the south-east. After a time, he had found a place for them to lie up. The land here was rolling hills, sometimes bunching into mountains. On the flank of one of these lay a hollow, deep and wide enough to hide eleven men and horses. There was a small stream nearby. As he rubbed down Pale Horse, the mount that Ballista had entrusted to him, Maximus approved of the Caledonian's choice. His hands working hard, he tried not to think about the grey gelding's owner; once his owner, now his patronus, the friend he had left behind.

Maximus had been woken the following morning by the sound of goat bells. Despite the many years since he had been taken as a slave out of his native Hibernia and brought to the southlands, goat bells somehow still sounded exotic. Although alien, they were usually reassuring, speaking of a gentle, timeless Mediterranean order. That morning, they had not been. They were drawing closer.

Looking round, Maximus saw that everyone other than old Calgacus was still asleep. The Caledonian was stretched out on the ground, peering over the lip of their hiding place. Maximus had scrambled up next to him and risked a quick look over the top. It was a small flock, no more than twenty head, strung out behind a lead animal. They were coming to the stream to drink. The purposeful tread of the leader would take them right by the hollow, would give the goatherd a perfect view of the fugitives.

Maximus had been surprised when Calgacus gestured for him to go to the far end of the hollow. The goats were close, the tinkling of their bells loud. As Maximus moved past, two or three of the Dalmatians stirred. He motioned them to silence. In position now, he looked back at Calgacus.

Unhurriedly, Calgacus rose to his feet and stepped up over the lip of the hollow. He stood still, hands empty by his sides.

Pulling himself up, Maximus peeked over the top. Through the legs of the animals, he saw the goatherd. He was an elderly man with a huge beard and the air of a patriarch. He was leaning on a staff, calmly regarding Calgacus. The goatherd's untroubled manner suggested that ugly old Caledonians or even daemons popped up out of every other gully he passed.

'Good day, grandfather,' said Calgacus.

For a time the goatherd did not respond. Maximus had begun to wonder if he did not speak Greek. He was wearing baggy eastern-style trousers, but then, everyone in Mesopotamia did.

'Good day, my child,' the local replied at last. Maximus felt an urge to laugh building inside him.

'Is it safe to be out with the goats with the Sassanids all around?'

The goatherd considered Calgacus's question, weighing it up. 'I keep to the higher hills. The goats must drink. If the Persians see me, they may not kill me. What can you do?'

The local had his back almost completely to Maximus. Now the latter saw the point of Calgacus's silent instruction. Quietly, he stood. As Calgacus glanced over, he touched the hilt of his sword. There was a pause before the Caledonian gave a tiny shake of his head.

'May the gods hold their hands over you, grandfather,' said Calgacus.

With due deliberation, the goatherd turned his patriarchal gaze first on Maximus then back to Calgacus. 'I think they may do already.'

The staff tapped the lead goat on the rump. The herder turned to go. Above the swelling tinkle of bells, he called back, 'May the gods hold their hands over you, my children.'

Maximus stepped over to Calgacus. 'If they catch him, the reptiles will torture him. Not many men could keep a secret under that.'

The old Caledonian shrugged. 'What can you do?'

Maximus laughed. 'How true, my child, how true.'

'Shut the fuck up, and take the next watch,' replied Calgacus affably.

They had saddled up at dusk. With the true night came thousands of stars and the thinnest of thin new moons. According to the ways of his people, Maximus made a wish on the new moon, a wish he could never divulge, for certain to do so would spoil its purpose.

Calgacus had led them to the north-west. With two riders out in front, they took it easy. There could not be many miles to the Euphrates. Unless the Sassanids intervened, they would be in Samosata well before dawn.

They had been travelling for some hours, their hopes rising, when, as the malignant gods willed it, the intervention came. A Persian challenge, loud in the night. A cry of alarm, then further shouts in an eastern-sounding language. Calgacus circled his arm, wheeling the tiny column; everyone booted their horses. All around was the rattle of hooves, the ringing of equipment and, from behind, the roar of pursuit.

Maximus had sensed as much as seen the solid black line of an arrow as it shot past him, accelerating ahead into the night. A second later, he had heard the wisp of an arrow's passing. Momentarily, he wondered if it was another unseen arrow or the sound of the first. Shrugging this germ of a huge idea out of his mind, he slung his shield over his back. As he rode, it banged painfully into his neck and back. At this short range, an arrow would probably punch clean through its linden boards, but somehow its weight and discomfort made him feel a little better.

They galloped on, over the pale, rolling hills, round dark, up-thrust mountains, past gloomy vineyards and orchards, through burnt hamlets and by abandoned farms. They crashed through small, upland streams; their beds stony, the water no more than hoof-high.

It is hard to outride men in fear for their lives. The clamour of pursuit had dropped back, faded to inaudibility beneath the sounds of their own movement. One more rise, and Calgacus signalled a halt. All the men dropped to the ground, taking the weight from their horses' backs.

Maximus looked round, counting. There were too few men in the pale light, just seven of them. Four of the Dalmatian troopers were gone. Had they been killed? Had they been taken? Or had they chosen a different path, either heroically, to lead the Sassanids away, or out of ignorance and terror? Neither Maximus nor anyone else in the party would ever know. They had vanished in the night.

Calgacus had handed his reins to the Greek boy Demetrius and was walking back to the brow of the hill. Hurriedly, Maximus did the same. Keeping low, they gazed back the way they had come.

The Sassanids had not given up. Not much above half a mile to the north, strung out at no great interval, torches flared across the hills.

'Persistent fuckers,' said Maximus.

'Aye,' agreed Calgacus. 'Having lost sight of us, they have thrown out a cordon to sweep the country.'

In silence the two men watched the easterners ride over the hills towards them. The undulating line of torches resembled a great snake coiling sideways, a huge mythical draco.

'If they want to stay in touch with each other, they will have to go slowly,' said Maximus. 'It will be fine for us.'

'Maybe,' said Calgacus, 'but if they get close we will try the trick Ballista used the time we were chased before the siege of Arete.'

Memories jumbled into Maximus's thoughts: waiting in a stand of trees down by the river, the smell of mud, a scatter of stones, a desperate fight in a gully.

'When Romulus died,' said Calgacus patiently.

Maximus was grateful for the hint. Although the Hibernian had a high opinion of himself, it did not run to priding himself on his powers of recall. On that occasion, Ballista had tied a lantern to a packhorse. His standard bearer Romulus was to lead the Persians away while the rest of Ballista's men rode to safety. After a time, Romulus was to turn the packhorse loose and make his escape, but something had gone wrong. He must have left it too late. Antigonus had come across Romulus a few days later – or what was left of him – staked out and mutilated. It had not ended well for Antigonus either: not long afterwards, a stone shot by a siege engine had taken his head off. Now, Maximus felt a rush of pity for his companions who had been lost along the way. He steadied himself. As he had sometimes heard Ballista say: Men die in war. It happens.

The seven remaining horsemen had pushed south. They rode hard, but not flat out. The stars wheeled and the moon tracked across the sky. There was no need for dangerous tricks with lanterns. Gradually, the lights of the Sassanids had fallen behind. After a time they could be seen no more.

Calgacus had kept them moving, when they could, avoiding the skyline, always aiming south-west. When dawn's rosy fingers showed in the sky, the elderly Caledonian had begun to hunt for a place to lie up. Eventually, when the sun was almost up, he turned aside into an olive grove which ran up the flank of a hill. They had dismounted and pushed through straggly vines and up under the trees.

The dappled sunlight was warm on Maximus's face when Calgacus shook him awake. Unnecessarily, the Caledonian had put his finger to his lips. Silently, Maximus rose and followed him to a space where the gnarled silver-grey trunks were more widely spaced. They looked down to the valley floor.

One thin column of dust followed by a wide, dense one. A solitary rider was being hunted down by at least thirty horsemen. No one in the olive grove spoke. In the randomness of his fear, the hunted man was riding directly towards them.

'The eye of Cronus is on us,' muttered Demetrius. The others said nothing. As the fugitive drew closer, they saw that he wore a light-blue tunic.

'Gods below,' said Maximus, 'it's one of ours.'

The lost Dalmatian trooper was almost in arrow shot when his horse stumbled. The man lost his seat, slid forward down the animal's neck. Trying to regain its balance, the horse plunged. The trooper fell. His momentum made him bounce once, high in the air, then, limbs flailing, he crashed to the ground. He scrabbled to his feet, his pursuers surging all around him.

There was a moment of stillness: the Dalmatian stood, the Sassanids in a ring around him. The trooper's horse ran away to the right. One of the Sassanids followed to catch it.

Slowly, almost apologetically, the trooper drew his sword. He threw it down. The mounted men laughed. One spurred forward. The trooper turned, started to run. A long blade flashed in the sun. There was a scream, a spray of bright blood, and the Dalmatian fell. The Sassanid cantered back into the circle. The wounded man got to his feet again. Another horseman rushed in. Again the flash of a blade. More blood, and again the man went down.

Maximus looked across at Calgacus. The Caledonian shook his head.

After the third pass, the Dalmatian remained on the ground, curled up, his arms covering his head. Their sport spoilt, the Sassanids called out insults, imprecations. Their prey remained down in the reddened dust.

The Sassanid who had gone to the right returned, leading the trooper's horse.

One in the ring of horsemen called an order, and the men unslung their bows. Another word of command and they drew and released. Almost as one, the arrowheads thumped into the Dalmatian's body.

The watchers on the hill had not moved.

A Persian slid from the saddle. Tossing his reins to a companion, he walked over to the corpse. With his boot on the body, he pulled out the arrows. The shaft of one had snapped; the others he handed back to their owners. The riders laughed and joked, teasing each other about their shooting. One carefully tied back his long hair with a bright strip of material.

Maximus became aware of his sword in his hand. He had no memory of unsheathing it. He held it behind his back so that it would not catch the sun. He forced himself to look away, at the others. Their whole attention was on the foot of the hill. They were all willing the enemy to leave.

Finally, when the watchers had thought they could bear no more, when even discovery and doomed violence had seemed better than the agony of waiting, a Persian shouted a word of command. The easterner on foot remounted, and the troop trotted off the way they had come.

Around him, Maximus had heard several men exhale noisily. He realized that he was one of them. 'Bastards,' he said.

Calgacus had not taken his eyes off the Sassanids. 'And would our boys have behaved better?'

Maximus shrugged.

It had not proved easy to sleep having just seen one of their commilitiones killed in cold blood, his butchered remains lying in view. Calgacus had moved the men further up the hill. It had done no good. A careless glance through the green leaves still revealed a glimpse of soiled blue tunic. The Greek youth Demetrius had said they should retrieve the man's body, offer him proper burial, at least a coin for the ferryman. Calgacus had overruled him. The Persians might return, they would be suspicious. But, Demetrius had argued, others might be drawn to the sight. Calgacus shrugged: it was the lesser of two evils.

Twilight had found them more than ready to move. Calgacus had outlined the new plan. Since the gods clearly did not care for the idea of them reaching Samosata in the north, they would go west to Zeugma. They would soon come to a broad, high plain, almost twenty miles across, then a range of hills from which the Euphrates would be visible. They could do it in one night. Once in Zeugma, they would be safe. They had passed through the town on the march out. Its walls were sound, manned by the four thousand men of Legio IIII Scythica and another six thousand regulars. Best of all, they were commanded by the ex-consul Valens, and he was no friend of either the Sassanids nor treacherous bastards like Quietus, his brother Macrianus and their scheming father Macrianus the Lame.

Calgacus had been about to give the word to set off when, boots slipping in the powdery soil, Demetrius ran up through the trees. When he reached them, he doubled up, panting like a dog after a run in the hot sun. One of the troopers, a good-looking man, helped him up into the saddle.

'Just a coin, a handful of dust.' Demetrius spoke to Calgacus, his tone defensive. 'I know if the reptiles come it will show that we have been here. But I had to. I could not let his soul wander for ever.'

Calgacus just nodded and gave the word to move out.

It had taken much longer to reach the plain than the Caledonian had suggested. When they did, it seemed to stretch on without end. On and on they had ridden, the stars high above as distant and heartless as the eyes of a triumphant mob. On either side, flat, grey nothingness. The men were bone-tired. They had lived with constant fear for too long. In the face of the plain's immensity, even Maximus had felt his composure slipping, his mind summoning up ghastly imaginings. After a time, it had seemed to him that it was the plain that moved while they stood still. It was like those stories Demetrius told: they were already dead, their sins on earth had been judged. They had been sent to Tartarus and it was their fate to ride this dark plain for ever, never reaching safety, never again seeing the sun.

Yet the grey light of pre-dawn had come all too soon. It revealed the hills in the west, but they were still a way off. All around them lay the emptiness of the plain. There were a few shrubs, the odd wind-bent tree; nothing to hide them. About a mile ahead, stark and incongruous, was a lone building. Anyone with any pretensions to fieldcraft knows not to hide in a solitary building; it is the first place searchers will look. Nevertheless, Calgacus led them straight towards it. There was nowhere else.

The building was a large, rectangular mud-brick barn. It had contained animals and people but now it stood empty. They led their horses in by the one, wide door. Inside, they hoisted a lookout up on to the beams. Some of the tiles were missing; Calgacus pushed out a few more in order to be able to see all around. The elevation increased the depth of his view. The other men rubbed down their horses and searched for food. There was none. There was a well outside, but there was always the possibility that it might be poisoned. They still had water in their bottles, but they had eaten their last scraps of food the night before. They could cut grass for the horses, but the men would have to go hungry.

Maximus had taken the second watch. He had to shift around the roof to keep an eye on all approaches, and it was just as well: falling asleep would bring with it the risk of a nasty fall. Another of Demetrius's stories floated into the Hibernian's mind. On Circe's island, one of Odysseus's crew had fallen asleep on the roof of the palace. He had tumbled off and broken his neck. Sometimes when Demetrius told the story, the man had been bewitched and turned into a pig. There was a thought – roast pork: hot, blistered crackling, the fat running down your chin. Infernal gods, Maximus was hungry.

Somewhat distracted by the demands of his stomach, it had taken Maximus a few moments to take on board what his eyes were seeing. The peasant couple with the donkey, the man riding, the woman walking behind, were quite close by. Maximus dropped down from the beams. He woke Demetrius and gave him a leg-up into the roof. Turning, he found Calgacus on his feet. A word or two of explanation passed between the two men, and they walked outside.

At the sight of the strangers, the peasant stopped his donkey with a word and his wife, her eyes downcast and inattentive, with a stick. His tattooed face registered no surprise. Like the goatherd the other day, thought Maximus, they bred them incurious out here.

'Good day, grandfather,' Calgacus said in Greek.

The peasant replied with a muted flow of words in a language neither of the other men understood. Now they were closer, they could see that it was not tattoos on the man's face but dirt ingrained in every line.

Maximus tried a greeting in Persian. An emotion seemed to run across the peasant's face. It was gone before Maximus was even sure it had been there. Quietly the woman began to sob. The peasant hit her with his stick.

With gestures and broken sentences in a range of languages, Maximus asked if the couple had any food. The man's response, which involved much eloquent waving of hands and minimal grunting of incomprehensible words, was an extended denial. As far as Maximus could make out, riders had come from the east; they had taken all the food, beaten the peasant and his wife. They had done something else, too, taken something, a child. Boy or girl, it would have not gone well for them.

The woman started to weep again. She quietened at the sight of the stick.

Calgacus invited them into the barn. The peasant made it clear that he and his wife would remain outside.

There they sat, hands on their knees, up against the wall of what could well have been their own home. As the sun arced across the sky, they moved around to keep in the shade. At intervals, the woman wept. Depending on how his emotions took him, the peasant would either soothe or threaten her. Maximus spent much of the day watching them, grieving for their naked misery. Even a man of violence such as himself could sometimes see the evil, naked face of the god of war – Mars, Ares, Woden, call him what you will: war is hell.

As the day faded, the men had tacked up, led their horses outside and swung into their saddles. Calgacus led them off to the west. Neither the peasant nor his wife showed any emotion at their departure.

Finally they had reached the hills. Finding an upward path despite the darkness, they took it. As the rocky slopes cut down their vision, they proceeded cautiously, placing two men out on point duty, fifty or more paces in front. And then they had come across the Persians.

Maximus looked away from Calgacus and back down at the enemy. The Sassanids were relaxed, perfectly unaware that they were being observed. They stood around where the three paths met, passing a wineskin back and forth. One of them raised his voice in song: ' Dreaming when Dawn's left hand was in the sky I heard a Voice within the tavern cry, "Awake my Little ones, and fill the Cup "Before Life's Liquor in its Cup be dry."'

The Persians laughed.

That's it, you goat-eyed bastards, thought Maximus, drink up every drop. Before Dawn's left hand is anywhere in the sky, in the next quarter of an hour, if you don't move, we are going to try and kill you – and we want you as drunk as possible when the sharp steel gets close.

Even if they did move, it was quite likely there would be a fight. If the Sassanids took the path to the north, all well and good. If they went west, the Romans might hope to follow and, once out of the hills, somewhere down on the narrow plain before the Euphrates, slip past into Zeugma. But if the Sassanids rode east, then there was no choice, there must be bloodshed.

One of the dark-grey shadows changed shape: a Persian leapt up into his saddle. He too sang, a voice less mellifluous than that of the first, but with a ring of authority: ' And, as the cock crew, those who stood before The Tavern shouted – "Open then the Door! "You know how little while we have to stay, "And, once departed, may return no more. "'

The Sassanids all mounted. They milled, sorting themselves into position.

Maximus, palms slick, held his breath.

The eastern troop clattered off to the north.

Demetrius, as so often, was at the back holding the horses. As well as his own and Calgacus's mounts, he had the reins of the grey gelding Ballista had insisted that Maximus ride. In the near-darkness, every time Pale Horse shifted, stamped a hoof or just breathed loudly, thoughts of the animal's owner crowded, insistent and importuning, into Demetrius's mind. There was pity, a terrible aching pity, for the big blond barbarian who had once owned the young Greek as surely as he had owned the horse. And there was gratitude. Enslavement and his first three years of servitude were things Demetrius preferred not to think about. It had been such a bad time that usually he found it easier to give out, sometimes even to pretend to himself that he had been born into slavery – if you have known nothing else, how can it be that bad? After three years he had been purchased as a secretary to Ballista. The big barbarian had treated him well for nine years. He had given Demetrius no reason to dwell on the old saying 'A slave should not wait for his master's hand.' Finally, four days earlier, on a burnt hillside, surrounded by the remnants of a defeated army, Ballista had given Demetrius the thing he wanted above all others: his freedom.

A noise from further up the path brought Demetrius back to the fearful present. He could see nothing. The narrow upland path was blocked by the remaining four Dalmatian troopers and their horses. The stars and young moon gave little light. Suddenly, there was a rattle of dislodged stones. Fear rose inside him, gripping his throat as he watched the troopers ready their weapons.

'Easy, boys.' Maximus's words were soft. The troopers relaxed. Demetrius sighed with relief.

They mounted up and got moving. They rode across a small meadow where three paths came together. Demetrius balled his fist, thumb between index and forefinger, in a symbolic gesture to avert evil. Crossroads were always bad places; you only had to think of Oedipus encountering his father. A crossroads where three paths converged, and darkness; it was hard to imagine a situation more likely to draw the terrible three-headed goddess Hecate or her dreadful minions up from the underworld.

After they had traversed the meadow, the hills rose up again. In the unearthly light, the white rocks and black shadows rendered the slopes into shattered or crazed mosaics. Demetrius rode just behind Calgacus and Maximus. He felt safer near them. The soft gleam of Pale Horse sent his thoughts back to Ballista. How had it gone for him at the hands of the Persians? The northerner had defied Shapur the King of Kings for months at Arete, had slaughtered thousands of his warriors below the city walls. He had routed a Sassanid army at Circesium – the waters of the Chaboras had run red with eastern blood. Worse, much worse, he had defiled the sacredness of fire, which the Zoroastrian Sassanids worshipped, by burning the corpses of their dead after the battle. It was unlikely things had gone well for him.

Maximus and Calgacus had their heads together and were muttering low. The Hibernian pulled Pale Horse out of line. As he passed, Demetrius smiled over. Maximus made no response; his eyes were far away, as distant as those of a distracted child. The grey horse standing there turned Demetrius's thoughts yet again to Ballista. On that scorched hillside, moments before they had left, Ballista had embraced Maximus, had whispered something in his ear. The Hibernian had promised he would die before he let anyone harm Ballista's two sons. At the memory, Demetrius felt a stab of jealousy. He pushed it away as unworthy. He was not a fighter. He did not have man-killing hands. Of course Ballista would ask his old companion in arms to put his body between the hostile blades and the bodies of his sons. Isangrim had just turned eight and Dernhelm was not yet two; both were beautiful, and both now fatherless.

A flash of movement to his right caught Demetrius's eye. He stared hard. Nothing: just rocks and shadows. He was looking away when he glimpsed it again. Yes, there it was. High up on the slope. About a discus throw away. A movement. Then he saw it clearly: a dark figure, a man on foot moving parallel to them.

Demetrius looked round at his companions. No one else seemed aware of the follower on the hill. Maximus was nowhere in sight. When Demetrius looked back, it took a few moments to spot the shadow again. There he was. Shabby, grey-black clothes, with maybe a hint of red. He flitted from rock to rock. No noise came down from him. With a chill in his heart, Demetrius saw the follower's face was dark, terribly dark. It was black. Grey-eyed Athena watch over us, he mouthed. This was no mortal that stalked them but a daemon or ghost.

Some ghosts were thin, insubstantial wraiths. If you tried to grab them, they slipped through your arms like smoke. Such ghosts were an annoyance, but they could not harm you. The daemon on the hill was not one of them. This ghost was one of the terrible ones. This was an embodied daemon, something terrible and dangerous, something like Lykas, who had slain old and young alike in Temesa; like Polykritos the Aitolian, who after nine months had risen from his tomb to seize his hermaphrodite son and tear him limb from limb, then devoured his body.

Demetrius fought down the rising tide of horrible ghost stories within him. Sometimes wide reading and a retentive memory could be a curse. He peered wildly about. The faces of the others betrayed nothing. Where was Maximus?

Demetrius, urging his mount forward to come alongside Calgacus, gazed again at the thing on the hill. As he did so, it changed shape, dropping to all fours. Swiftly, it ran like a wolf or a dog to the next cover. From out of the darkness, clear even above the noise of the horsemen, came the bray of a donkey. The beast reared up, briefly standing on two legs – looking around, sniffing the air – before slipping to the ground and slithering like a snake behind a rock.

Pallas Athena and all the gods of Olympus hold your hands over us. Demetrius was too scared to pray out loud. This was worse than a daemon. Far, far worse. They were being stalked by a shape-changing empusa, one of Hecate's ghastly servants from the underworld. Hecate, the dark goddess, none of whose desires were ever denied by Zeus.

Demetrius had read in Philostratus that the holy man Apollonius of Tyana had once routed an empusa with just a shout. Demetrius was too scared to shout. Anyway, would a shout not bring the Sassanids down on them?

The young Greek leant over, almost overbalancing from the saddle in his anxiety. He grabbed Calgacus's arm.

'Quiet, you young fool,' the Caledonian hissed.

Eyes wide, Demetrius gazed, silent but uncomprehending. Why was Calgacus doing nothing? Where was Maximus? Why did these barbarians not do something? Had they no concept of what an empusa could do?

As they rode slowly on, Demetrius saw that Calgacus was watching the thing on the hill out of the corner of his eye. The Caledonian was rigid with expectation. His mount tossed its head as it sensed the tension.

Up on the hill, higher up the slope, there was another movement. Another dark shape slipped over the skyline. It crept slowly down towards where the first was hidden.

Could there be two of the creatures? Darkness, fatigue and fear were taking their toll on Demetrius. Gods below, what if the things hunted in packs?

The first dark shape must have heard or sensed something. It suddenly stood and scanned the hillside. Then, quick as a flash, it sprang and raced away to the west. The other figure leapt up in pursuit. Stones slid out from under their feet. Dislodging others, they bounced in showers down towards the path.

Calgacus booted his horse. It clattered down the path. After about fifty paces, the Caledonian brought it skidding to a halt. Belying his age, he threw himself off its back, tugged a couple of javelins from the holster on the saddle and started up the slope to cut off the fugitive.

Seeing the new threat, the fugitive tried to veer back up the incline. It was no good: the second figure was already in position, ready to block any escape in that direction.

Like Celtic hounds, the two pursuers coursed their prey over the stony slope. They turned him this way and that, ever closing.

'Stop or I will run you through,' Calgacus yelled in Greek. His prey raced on. The old Caledonian drew back his arm and cast a mighty throw. The javelin winged over the fugitive's shoulder. A spark flashed as it glanced off a rock.

The fugitive pulled up dead in his tracks. Calgacus grabbed his arms, twisted them behind his back, pushed him down towards the waiting horsemen.

Maximus rejoined the men moments later. 'Fuck, that nearly killed me,' he panted.

Relieved beyond words, Demetrius studied the prisoner. No feast for the eyes, but he was no daemon or empusa: he was a small man, face blackened, wearing the pelt of a dark-grey wolf and a cap of weasel skin. He too was breathing heavily.

Quickly and efficiently, Maximus searched the prisoner for weapons. Finding none, he stepped back and kicked the man's legs from under him.

'Don't kill me! Dear gods, please don't kill me!' The man spoke in Latin. It was oddly accented, like something unpractised. He was terrified. He cowered on the ground, teeth chattering.

'Courage,' said Maximus. 'Death is your last worry.'

'I am just a soldier, a Roman like you. Please don't kill me!'

'Name? Rank? Unit?' Maximus snapped out the questions.

'Titus Esuvius, miles, Legio IIII Scythica. Don't hurt me.' The words tumbled out.

'You are a deserter.'

'No, no, Dominus, a scout. I am a scout.'

'What are you doing out here?'

The prisoner gulped. 'Just trying to get back to Zeugma. Please, take me with you.'

'Where have you come from?' Maximus's questions were relentless.

Again the swallowing, the slight hesitation. 'From the field army. Please, take me with you.'

Maximus glanced at Calgacus, jerked his head. The Caledonian roughly hauled the prisoner to his feet, pinned his arms behind his back. Maximus drew his sword. The blade of the short gladius shone in the pale light.

'Time to tell the truth.'

The man sobbed. 'I am. Please believe me. I have a family, don't hurt me.'

'Tell me,' said Maximus, 'have you ever been drawn to eastern religion?' As he spoke, he moved forward and deftly, with one hand, unbuckled the man's belt.

Fear and incomprehension played across the prisoner's face. He shook his head. 'No, never. I don't understand.'

Two tugs and the man's trousers and undergarment were round his knees. 'No interest in, say, the goddess Artargatis? No yearning to take a trip to her temple at Hierapolis?'

Suspicion clouded the man's face. 'No, I… no, never.'

'Pity, considering what's going to happen to you.' Maximus reached out and grasped the man's testicles. With the other hand, he showed him the sword. The man whimpered. 'They make a good living, her devotees, the Galli. Of course, they castrate themselves. And I think they use a stone blade, flint most likely. But mutatis mutandis – if you survive, I'm sure they'll take you in.'

The man was making incoherent begging noises.

'Now, what is it to be? Are you going to tell me the truth, or is it off to Hierapolis for you?'

As if a dam had broken, the words poured out. 'My name really is Titus Esuvius. I was born in Lutetia in Gaul. I was with a cavalry ala. We came out east for the campaign of Gordian III. I… I did something wrong. I had to desert. Been with the Sassanids for years – married, got a Persian family. The Lord Suren himself ordered me to Zeugma to spy out the defences. What could I do? I had no choice. Please, let me live. I want to see my children again.'

The stream of words was cut off when one of the Dalmatian troopers led his horse up from the rear. 'The reptiles are coming.'

The prisoner wriggled free of Calgacus. He threw himself on his knees. 'Please, leave me here – bound and gagged – I won't tell them anything.'

'No more words.' Maximus's face was set.

Just as the man reached up a hand to grasp Maximus's chin in supplication, the Hibernian's sword swung. A flashing hack caught the prisoner square across the neck. Blood sprayed hot.

'Mount up,' said Calgacus.

Demetrius stood near the corpse with the half-severed neck. Maximus was cleaning his blade on the dead man's wolfskin.

'You promised him his life,' the Greek said.

'No, I said death was his last worry.' Maximus swung up on to Pale Horse. 'Is that not so for all of us?' They were riding flat out, the Sassanids hard on their heels. The thunder of their passing echoed back from the stony slopes on either side. At least it was simple, thought Maximus, just two choices: run or fight. No need to be thinking of clever tricks with decoys, lanterns or anything else. Nowhere to hide and nowhere to go but down the one track: just run or fight.

The track twisted and turned, rose and fell as it graded across the hills. It was narrow, the surface loose and uneven. The hooves of the horses scrabbled as they slid around sharp corners. More than once, riders had to grab the twin front horns of their cavalry saddles to prevent themselves being thrown. A couple of times Demetrius was nearly on the floor. The young Greek was no centaur. This cannot go on, thought Maximus.

'Ease up, Calgacus,' he called. 'The body of the spy will have delayed them. Ease up, or there'll be a fall, probably a pile-up.'

The Caledonian considered then brought his mount down to a fast canter.

Maximus looked up at the sky. The night was rushing on, not much of it left. But they must be getting to the edge of the hills. After that, just a small plain, four or five miles across, and they would be safe behind the walls of Zeugma.

The small figure was standing in the middle of the track as they came round the corner. Maximus and Calgacus pulled hard on their reins, thighs braced firm into the leather and wood of their saddles. They swerved round the obstruction as they drew to a stop. Behind was confusion. Demetrius's mount barged into the back of Pale Horse. Miraculously, no one had ridden down the child.

Maximus scanned the slopes all around. No movement. Nothing. It couldn't be a trap. He swung a leg over Pale Horse's neck and dropped to the ground.

The child was a fine-looking boy, about eight years old. He had a heavy, fine neck ornament. He was crying.

'My mother has gone. She was scared. She said I was too slow. She has gone.'

Maximus held out his arms. The child hesitated for a second. Maximus knew that his battered face, the tip of his nose missing, was unlikely to be reassuring. He scooped the boy up. The child buried his face in the Hibernian's shoulder.

'My father is on the Boule of Zeugma. He is a rich man. He will reward you.' The boy chattered in Greek.

'We best be moving,' Calgacus said.

Maximus put the boy on Pale Horse then jumped up behind him. They headed off.

They had not gone far when they heard the sounds of pursuit: high, keen cries, the low rumble of many horses. Calgacus pushed the pace. The horses were slow to respond. They were as tired as the men. These four days had taken it out of them all.

From the crest of a rise, Maximus glimpsed the flat, empty greyness of the plain below; it wasn't far ahead. As the track dropped down behind him, a trooper's mount stumbled. In its fatigue, it almost went crashing. If it had, it would have brought others down with it.

This is no good, thought Maximus. If we're out on the open plain on spent horses, the Persians will run us down as easy as catching mackerel.

The horses were labouring up a straight incline. It ran for about fifty paces. The hill on the left reared up into a small, sheer cliff. Stones fallen from its face were scattered across the track. Near the top of the incline, a sizeable pile narrowed the path to single file.

As good a place as any, thought Maximus. He pulled over, indicated to Calgacus to join him, and waved the others past.

'I think I'll be staying here a while.' Maximus jumped down. He unhooked his shield from the saddle. 'Change horses and take the child.'

Calgacus said nothing. Stiffly, he dismounted, collected his own shield and, while Maximus held the heads of both horses, climbed up on the grey gelding behind the boy.

'You sure?' Calgacus asked.

'Sure.' Maximus looked up at the Caledonian. 'Back before we left the army, I promised Ballista I'd look after his boys. That is on you now.'

'Aye, it is.' Calgacus did not meet Maximus's eyes. His gaze wandered over the face of the cliff.

The noise of the pursuit was clear.

'Say goodbye to Demetrius for me.'

'I will.' Calgacus untied the bowcase and quiver from Pale Horse's saddle. He threw them down to Maximus. 'Keep mine as well.'

The noise of the pursuit swelled.

Calgacus gathered Pale Horse's reins, turned his head and moved on. His eyes still did not meet Maximus's but continued to look here and there over the cliff.

Left alone, Maximus worked swiftly. He led the horse a little way beyond the large pile of fallen stones and, with a strip of leather, hobbled its front legs. He scooped up Calgacus's bow and quiver together with his own. He ran back and took his stand half behind the mound. He drew his sword and put it and his shield in front of him, near to hand on the ground. He propped up the quivers so he could easily reach the arrows, and the spare bow beside them. He selected an arrow, examined the straightness of its shaft, tested its point. Satisfied, he notched it, half drew his bow and sighted down the track.

As he waited, time played strange tricks on Maximus. It slowed down; stopped altogether. Each breath seemed to take an age. The noise of the Sassanids grew louder, but they did not appear. The sounds seemed to fade. Maximus relaxed the bow. He counted his arrows: twenty. He looked at the stars, as unknowable as the hearts of men. They were paling. It was nearly dawn.

The first two Sassanids took him by surprise. They turned the corner side by side, at a good canter. Maximus drew the bow. He aimed at the one to his right, deliberately low, intending to hit the horse. He released. Having grabbed another arrow, he saw the horse was down, its rider rolling in the dust. He shot at the other and missed. He shot again. The arrow buried itself into the horse's chest. The animal somersaulted forward, its rider catapulted over its head. He crunched hard into the stony path.

Another Sassanid had negotiated the first fallen horse. Sword out, he was urging his mount up the incline. Calmly, deliberately, Maximus shot him. The arrow plucked him off his horse's back. The smell of blood strong in its nostrils, equine cries of pain loud in its ears, the horse bolted up past Maximus and away.

The remaining Sassanids at the foot of the incline were at a standstill, unsure how many were against them, uncertain whether to go forward or withdraw. Maximus drew and released again and again. The deadly shafts whistled through the pale-grey light of pre-dawn.

An easterner on foot was rushing at him from the left. Maximus dropped his bow. He crouched to scoop up his sword and his opponent loomed over him. The Sassanid held his sword over his head in a two-handed grip. The long blade started to come down in a great sweep like an axe. Uncoiling, sword out in front, Maximus drove himself forward under the blow. The sharp point of the Hibernian's gladius drove into the stomach of the Sassanid. The two men were pressed together. There was a slaughterhouse stench. Maximus pushed the still-gasping easterner away.

The Sassanids drew back out of sight. Under his shield, peering round the stones, Maximus could see two dead horses and two dead men. Nothing else. He counted his remaining arrows: eight. He wondered whether to run for it. Had he bought enough time for the others?

No time now. A rising war cry. The Sassanids were coming again. Maximus put down the shield, sprang to his feet and drew his bow. The Persians thundered into sight. Maximus released. He grabbed another arrow. Working as fast as he could, he poured missiles down into the enemy.

An arrow sliced a hand's breadth past his head. This time, the easterners at the rear were shooting over the heads of the ones in front.

Maximus released again. A Persian horse went down. He shot once more. He missed. He reached for another arrow. There were none left. He took up sword and shield. There was no stopping them this time.

The Sassanids were almost on him. He could see the flaring nostrils of their mounts, hear the snap of the long streamers they wore. A small stone bounced off his helmet. He glanced up. A shower of stones was falling. Above that, the air was full of rocks.

Maximus turned and ran. Stones and rocks slewed off the ground all around him. One caught him a painful blow on the shoulder. Behind him there was an awful roaring, a grinding.

He had moved beyond the torrent of debris. Maximus stopped and looked back. The track was invisible behind a thick cloud of dust. He stood staring stupidly at it. Beside him, his horse whinnied, struggling against its hobble. Maximus walked over. He found he still had his sword in his hand. He sheathed it. He must have dropped his shield. He calmed the horse, untied its hobble, climbed on its back.

The dust had started to drift away: the track was almost obliterated under the landslide. The Sassanids were gone; either crushed or fled.

A noise above him made Maximus look up at the top of the cliff. An ugly face gingerly peered over the edge. Seeing the Hibernian, it broke into a huge smile.

'Try not to look so surprised. Who did you expect would save someone like you? Surely you don't think the gods love you enough to cause a landslide? I am not really sure I do,' said Calgacus. 'And now I have to find my way down again.'

His back to the wall, Ballista could not move. His thighs were pinned by those of two other men, the tribune Marcus Accius on his left, Camillus of the VI Gallicana on his right. Ballista could feel the heat coming from their bodies. His own was dripping with sweat. The air was thick and he was finding it hard to breathe.

Ballista had always feared confined spaces. The subterranean cell was tiny. The majority of the senior officers of the Roman field army had been pushed into it and there was barely enough space for them all to sit. Ballista badly needed to stretch his legs, to check his cut and bloodied feet, but there was no room.

The dignitas of Rome was humbled, the emperor Valerian captured, his entire army dead or surrendered. Almost all the high command had been herded like slaves into this stinking prison – almost all: Valerian and his ab Admissionibus Cledonius were not there. They had been taken elsewhere, to endure further humiliations, to be gloated over at leisure. And Turpio was not there either. He was dead. Ballista had taken a last look at his friend as they left the valley of tears, a last look at his decapitated head stark on a pike.

From somewhere in the crush of bodies came the voice of the Praetorian Prefect Successianus. 'Discipline, we must keep our discipline. These cock-sucking Sassanid reptiles do not know disciplina. Keep our disciplina and we can beat them.' Over and over he muttered it. Ballista thought Successianus might be losing his mind. If so, it would be no wonder.

The march south could have robbed any man of his reason. It had been two days of hell. The line of prisoners had been driven along by blows, from whips, the butts of spears and the flats of blades, sometimes the edges. Valerian had been at the head of the line, dressed as a slave, a crown of thorns digging into his aged head. His officers, loaded with chains, followed him. Their boots had been taken and they had stumbled as the sharp rocks tore their feet. Behind them had trudged the long tail of the rank and file.

It had been hot, unbearably hot. Overhead, the sun was merciless. Swirling clouds of dust had blinded them, lodged in their throats, threatened to choke them. They had been terribly thirsty. Once a day they had been driven like cattle to water. Many had not had a chance to drink before they were beaten onwards. Twice, rounds of stale bread were thrown to them. Some had been too far gone to eat; others had fought over these scraps.

Degradation had been added to cruelty. If a man fell out to relieve himself, the Sassanids amused themselves by jeering and throwing stones as he squatted. When a man collapsed, he was beaten to his feet. If he did not rise quickly enough, he was summarily killed.

The ordinary milites had suffered worse than the officers. No residual eastern respect for rank had protected them. If a young soldier's looks, not totally obscured by the dirt and suffering, happened to catch the eye of a guard, he was hauled out of the ranks. Held down, often in full view, he was raped, sometimes repeatedly. After the assault, the victim was left lying in the dirt. Some staggered back to the column; others remained prone in the dirt. Ballista had watched as one, a fresh-faced youth not yet twenty, covered his head and waited to die.

Not long after setting out, they had come upon a dry stream and the march was stopped. Glorious in purple and white raiment, with streamers floating behind, the Sassanid King of Kings had ridden up to inspect the stream. After consultation with some of his courtiers, Shapur had ordered a squad of legionaries to be forced down into the low watercourse. The banks had been ringed with horsemen. The Romans had fallen to their knees, arms out in supplication. It had done no good. To the accompaniment of mocking laughter, the defenceless men were riddled with arrows. An imperious order, a flurry of blows, and the column had been forced to march over the still-bleeding bodies of their comrades.

Towards the end of the first day, they reached Edessa. The white-walled city was still holding out. The ragged line of captives was halted within arrow shot, their abjectness displayed to the defenders. Near Ballista, a tribune had wept at the tantalizing closeness of safety.

Valerian had been escorted up to the eastern gate. Under duress, the elderly emperor had called for the governor. When he appeared, Valerian commanded him to surrender the city. High on the battlements, Aurelius Dasius put his fingers to his lips and blew a kiss. Having performed proskynesis, the governor snapped a military salute and wordlessly turned away.

The second day, they had been marched down to Carrhae. Across the flat plain, the city rose like a platform in the distance. Word ran down the column that Carrhae had opened its gates to the Persians.

A few miles short of the city, they were brought to a halt by the temple of Nikal, the bride of Sin. The sanctuary of the moon goddess and her powerful consort was a hive of peaceful activity. Under watchful Persian eyes, local priests scurried around the banks of the sacred lake. Soon a great fire was lit and a holocaust committed. It had been hard to choose which was the more tormenting, the smell of whole animals roasting or the sight of the unattainable clear waters of the lake.

A Sassanid noble had ridden up to the bedraggled Roman officers. Laughing, he had called out in Greek, 'See, we treat you, our honoured guests, like the gods. They too dine on the smoke of sacrifice.'

The ordinary milites had been left outside the city walls. The officers were marched under an ornate gateway, through streets where the citizens were encouraged to jeer and throw things, then manhandled into the cramped, airless cell.

'Disciplina…' In the gloom, the Praetorian Prefect's mutterings ran on. Ballista's legs were seized with cramp. Apologizing to Aurelian, the young Italian prefect wedged in front of him, Ballista painfully flexed them. He was weary to the bone. He wanted to shut his eyes, but he knew that when he opened them again the airless press of bodies and his inability to move would cause a wave of panic that might engulf him. On the march he had been glad enough not to be one of the rank and file, but now he would have given a lot to be with them. At least they had the night air on their faces and the delicious luxury of just a little unrestricted movement.

There was the screech of a drawn bolt, and the door swung open. Two easterners, long swords in hand, scanned the crush.

'Which one of you is Ballista?'

Unwillingly, Ballista raised his hand. This was not a good turn of events. The Roman general who had slaughtered so many easterners at Arete, had defeated a Sassanid army at Circesium and had then in their eyes committed the terrible sacrilege of burning their bodies could expect only harsh hospitality from the King of Kings.

'You come with us.'

It took some time for Ballista to get out of the cell. First he had to get to his feet. This involved levering himself up by using the wall. Then the Roman officers had to clamber on top of one another, all dignitas dispelled, to clear a path.

As the door shut, Ballista heard Successianus. 'Disciplina, keep your disciplina,' the Praetorian Prefect repeated.

Fuck you and your Roman disciplina, Ballista thought. I was born a warrior of the Angles. We have our own ways of facing down fear. Allfather, Deep Hood, Death-blinder, Woden-born as I am, do not let me disgrace myself or my forefathers.

Two guards took Ballista's arms. Two more, weapons drawn, followed. Ballista felt the cuts on the soles of his feet open as he shuffled along. The chains fastened to his ankles threatened to trip him at every step. Movement made the manacles on his wrists and the weight of the chain that linked them hurt like all hell.

He was hustled along corridor after corridor through the palace cellars. At first he tried to memorize every turn. Then he realized he had forgotten the route they had taken in getting to the cell. After that, he concentrated on not giving way to his fear.

The guards opened the door to another cell. They pushed him inside, surprisingly gently. He did not fall full length, merely staggered. The door was shut. The bolts slammed.

Standing still, Ballista took stock. The cell smelled musty but clean. There were no windows, so it was completely dark. Squatting into position for an ungainly crawl, Ballista explored his new prison: about six paces by six, bare earth floor, rough stone walls, nothing movable, nothing that could be used as a weapon.

With a grunt of effort, Ballista settled himself against a wall. He tried to make himself as comfortable as possible, easing the metal away from the abrasions and sores on his wrists and ankles. Now he was alone he missed the companionship of the other officers. At least they had all been in it together.

Ballista was tired. His fatigue was a mine that each of the last two days had dug deeper, the tunnel burrowing away from the light, the air even harder to breathe. He thought of Julia, his wife, of Isangrim and Dernhelm, his two beautiful sons. He imagined their pain when news reached Antioch of the disaster. If he died, would they ever hear of it? Or would he just be gone, his end an empty space their minds would fill with terrible tortures and pain?

Shutting his eyes, Ballista promised himself that if there were a chance – no matter what it took, no matter at what cost to himself – he would get back to them.

The door crashed open and Ballista was temporarily blinded by the light. Two easterners entered and put lamps on the floor. Someone laughed outside. The door shut. Ballista peered up at the two men. The younger, he half recognized. The man was dressed in the garb of a Persian nobleman, his face made up, kohl around his eyes. He exuded a smug air of self-controlled menace. The older wore more outlandish clothes, a jacket with empty, hanging sleeves and a fur cloak, and had strange braids in his hair. Ballista did not know him. The stranger stepped over to Ballista and kicked him. The blow landed on his arms. The man shouted something in a language Ballista had never heard and kicked out again.

'On your feet,' the Sassanid by the door said, in Persian.

Ballista stayed where he was. He peered out from behind his raised arms, trying to look confused, helpless. 'Latin, I only speak Latin.'

The Sassanid moved from the door. He leant down, bringing his face close. He did look very familiar. Smiling unpleasantly, he spoke. 'We have met before. The first time, at Arete, your excellent command of my language tricked me into letting you escape. I vowed there would be a reckoning. The second time, not long ago, your status as an ambassador robbed me of my revenge.'

Ballista remembered now: he was Vardan, son of Nashbad, a captain in the service of the Lord Suren. Wherever you go, old enemies will find you. And Woden knew, Ballista had made enough of them.

As Ballista got up, Vardan grabbed him from behind, pinioning his elbows to his sides. The manacles dug into Ballista's wrists, the chain between them drew tight across his stomach.

'Be assured, northerner, nothing can save you tonight,' Vardan hissed, his breath hot in Ballista's ear. 'We have the whole night. My revenge and pleasure will be sweet as they come together.' Vardan laughed. 'But first…'

The other man spat in Ballista's face. He began to shout furiously, the unintelligibility of the words to the northerner making them more frightening. The man spat again. His breath was heavy with spicy food and strong wine. This man was full of hatred, but Ballista had no idea why.

The man stepped back and removed one of his slippers. Screaming what was abuse in any language, he beat Ballista around the head with it. Even though the slipper was light, it hurt. The frenzied attack went on until Vardan said something in the incomprehensible language.

Vardan again whispered in Ballista's ear. 'This is Hamazasp, King of Georgian Iberia. You killed his son at Arete.'

Vardan spoke again. The language must be Georgian. Hamazasp laughed. He began to unbuckle his belt. 'Do not worry, barbarian, you will not have to live with the shame for long.' He smirked. 'Afterwards, we will kill you.'

Ballista threw himself backwards, smashing Vardan into the wall. The Persian wheezed as the impact forced the air out of his lungs. Ballista stamped his left heel down on Vardan's foot, making him howl.

Hamazasp was bent forward, fumbling his trousers up. Ballista lunged and hooked the chain of his manacles over the Georgian's head. Pulling him close, Ballista drove his right knee up into his crotch.

As Hamazasp doubled up, Ballista freed the chain and spun round, swinging it with him. The hard metal links snapped into Vardan's face. There was a scream, blood sprayed and the Persian staggered sideways.

The door was thrown open. Ballista rushed at the guards. The chains around his ankles tangled in his feet. He crashed forward on all fours. Scrambling, he tried to rise. A savage kick caught him under the chin. His head snapped backwards. There was a blinding flash of light, a roaring sound in his ears.

Something animal makes the body defend itself, even when the mind is dazed. Ballista found he was curled up on the floor, arms trying to shield his head. The kicks were hard, shrewdly aimed. One after another they came, in his kidneys, stomach, mouth, ears. Ballista felt blood pouring from his nose. His mouth was full of shattered tooth fragments. Relentlessly, the beating continued.

'Enough.' Vardan's voice seemed to come from miles away. The kicking stopped.

Ballista lay, muscles twitching, stabs of pain flickering through him. Several men seized him. He was rolled face down. His limbs were stretched out. Hands hauled up his tunic, gripped the waist of his trousers.

'Stop!' A voice new to the room, Persian but distantly familiar.

'This is nothing to do with you priests, Hormizd.'

'The great god Mazda has willed that everything is the concern of his mobads.' The voice was controlled but tight with emotion. 'I am sure that neither you, Vardan, nor the King of Georgia would be so unrighteous as to deny that the caste of warriors must abase itself before that of priests.'

There was a charged silence that seemed to indicate unwilling acquiescence.

'Even should you have been led so far astray by Ahriman the Evil One, it would be unwise for a vassal king or an officer in the service of the Lord Suren to ignore the will of the Mazda-worshipping King of Kings.' The voice was growing in command, becoming mellifluous. 'Shapur himself, may his name be praised, has commanded the prisoner called Ballista be brought before him at the first audience of the day, as soon as the pious King of Aryans and non-Aryans has performed the rites that greet the dawn. Now my servants will take charge of the prisoner. You may go.'

Ballista heard the men leave the room, their footfalls and mutterings dwindling down the corridor. Spitting out tiny bits of tooth, painfully, he turned over. A young man with an earnest face and a big beard was bending over him. Ballista ran his tongue over his split lips. Croakily, he spoke.

'Greetings, Bagoas. It has been a long time.' Ballista lay in the warm waters of the tepidarium. It had been agony getting in – the grazes had stung even sharper than the cuts – but now the water was supremely soothing. It was scented with carnations and cloves. Relishing the seclusion of the small private bath, Ballista checked his physical condition. His wrists, ankles and the soles of his feet were badly cut from the march. The rest of his body was covered in bruises and abrasions. He squinted into a small, highly polished metal mirror, which kept steaming up. His right eye was blackened, the left almost closed. His front teeth were broken; some at the back ached abominably. But apart from a stabbing pain in his left side when he moved – probably a cracked rib or two – he did not seem to have any broken bones. He was battered and exhausted yet, if a chance came, he could still run or fight.

A door opened and the young priest entered.

'Thank you, Bagoas… sorry – Hormizd.' The Persian youth smiled slightly in acknowledgement of the correction. 'You know,' Ballista continued, 'when you first joined my familia in Delos, I thought you were lying when you said that was your original name.'

'The idea had crossed my mind. I had no wish for anyone to know from what family I came before I was captured. Now the time of my servitude is something not spoken of at court. The divine King of Kings has declared that it should be as if it never occurred. It is as unmentionable as those traitors condemned to the Castle of Oblivion.'

'Why did you save me?'

'Such things are an abomination. When I was… with you, your men Maximus and Calgacus saved me from the same fate.'

'Thank you. But you had already repaid the debt. Maximus told me that you sent our pursuers on the wrong path after the fall of Arete.'

Hormizd smiled, his even teeth very white behind his black beard. 'One who seeks to be a virtuous man does not wait to incur a debt before doing good.'

'I am sure. But now I am in your debt. Although it is hard to imagine how I could be in a position to repay you.'

'One can never tell what great Mazda holds in store for a man,' Hormizd said seriously. 'Now, let me wash your hair. Talk is more free without servants.'

The young Persian knelt by the bath. His fingers worked carefully around the cuts on Ballista's scalp as he cleaned the northerner's long hair.

'Tell me,' said Ballista after a while, 'why does Vardan hate me?'

'For the loss of his jewelled hair-clip.'

'What?'

'The King of Kings gave it to him. After you tricked Vardan into letting you go outside Arete, it was taken back. I imagine that every time someone dresses Vardan's hair, the hurt rankles.'

Ballista laughed. 'The old Greek Herodotus was right: everywhere, custom is king.'

'Come, let me help you out of the bath. I will call my servants to dry you. There is time for a few hours' sleep before you are taken to the King of Kings.'

'Shapur really wishes to see me?'

'Yes.'

'Why?'

'That is not for me to say.' It was dark, a warm Mesopotamian spring night. Ballista was taken out on to the top of the citadel of Carrhae. At the eastern end of the terrace, off to one side, stood two iron tripods. Cledonius was sitting on one of them. Ballista was led to the other. He sat down with relief. Even in delicate silk slippers, it hurt to walk. As Ballista waited, he watched the eastern sky slowly pale to an eggshell blue.

The King of Kings came out of the palace and stopped in front of the high golden throne. The entourage that flanked him arranged itself into two divisions. On his left were the priests, on his right the high nobility and his client kings. Among them, Ballista saw, was Valerian. The Roman emperor stood some way from Shapur. The King of Iberia, Hamazasp, was significantly nearer the throne.

The great orb of the sun broke the line of the distant hills. Gracefully, the King of Aryans and non-Aryans sank down until he was full length on the ground, prostrating himself before the newly risen deity. There was complete silence as, from the very tips of his fingers, he blew a kiss. Then he stood up.

A pure white stallion was led before Shapur. High-stepping, its neck arched, the beautiful Nisean went consentingly to its fate. The King of Kings rubbed its nose, whispered into its velvet ears the message it would take then, suddenly, struck the sharp blade deeply into the base of the stallion's neck. With the deftness of long practice, he swiftly pulled the knife out and stepped to one side. A stream of blood as thick as a man's arm spouted out.

The horse stood quite still as its life blood pumped away. Everyone watched. For what seemed a long time, nothing moved, except for the gushing blood and the spreading dark, cloudy pool. Then, without preamble, the horse collapsed.

When the horse was dead and the communion between Shapur and his god complete, all the members of the court, Valerian included, performed proskynesis.

Shapur settled himself on the throne. A scribe moused forward. Giving the impression of keeping low to the ground, he began to read from a book. Although the Persian king's hands toyed with a strung bow, his eyes were attentive. The sound did not carry, but Ballista knew the dibir was reading the words spoken by Shapur the night before when he had been drinking.

At length the scribe had finished and was dismissed. Ballista and Cledonius were gestured forward. They got down on their bellies by the carcass of the horse, the smell of its blood strong in their nostrils.

'Rise.' The Sassanid king's jewels and crown glinted in the morning sun. His dark, kohl-lined eyes regarded them.

'But what is to be done? The will of heaven must be endured.' Shapur recited the Greek verse with but the slightest hint of an eastern accent. Recognition swam just below the surface of Ballista's thoughts.

'But how to ask what I want to know without causing you any pain, that is my dilemma. And yet I long to be satisfied.' Shapur raised his hands in mock-uncertainty.

Cledonius replied. 'No, ask your question; leave no desire unfulfilled. Your wishes are also what my own heart desires, Great King.' Only the title broke the metre.

Shapur smiled. He pointed his bow at Ballista. 'And does a barbarian from the quarter of the world not to be named by the pious know the works of the troglodyte of Salamis?'

'A man has to bear the senseless acts of his rulers.' As Ballista finished the quotation from Euripides, a terrible stillness spread across the terrace.

Shapur clapped his hands, threw his head back and laughed. Quickly, but more quietly, those around him joined in.

'The power of Euripides transcends all.' The courtiers fell abruptly silent as the king spoke. 'Last night, we diverted ourselves with his poetry. Everyone finds what he wishes in it. Truly, there are as many interpretations as readers.' The long line of heads nodded to acknowledge the profundity of the monarch's words.

'Now to affairs of empire.' Shapur still spoke in Greek, but his tone became brisk. 'It was the will of heaven for me to capture in war, to seize with this, my right hand, the emperor of the Romans. Now my prisoner Valerian begs for me to reinstate him on his throne. It is his heart's desire to become my vassal. He wishes to arrange his ransom.'

Out of the corner of his eye, Ballista looked at Valerian. The heavy old face was immobile.

'Valerian assures me that no one has more influence with the crippled servant he left in charge of those troops fortunate enough to have remained in Samosata than the two of you.' Shapur paused. 'As a messenger to Macrianus the Lame, the name of Cledonius was received with pleasure by my ears and those of my court. Who could be more fitting for the task than the faithful doorkeeper, the man who once said come and men came, who said go and they went.' A polite titter at the king's playful words ran through his entourage.

'But many were shocked, no – many were angered at the name of Ballista, the unrighteous man who offered me futile defiance at Arete, who tricked my loyal warrior Garshasp the Lion into defeat at Circesium, who there defiled the purity of fire with the corpses of the slain. Even our majesty was surprised when the mobads led by Kirder our high-priest spoke in favour of letting you go.'

Ballista glanced at the priests. There were two distinct groups, one ranked around a priest with a long nose and a jutting chin, with Hormizd standing at the shoulder of what must be Kirder the Herbed; the other gathered about a figure wearing a sky-blue cloak, yellow-and-green-striped trousers and carrying a long ebony cane. Between the two groups there was a palpable animosity. In every monarch's court there are factions, Ballista thought.

'Yet the arguments put forward by Kirder and the mobads were telling,' Shapur continued. 'A man to whom Mazda has not shown his face cannot know the ways of righteousness. How could a barbarian born in the cold quarter of the world where lies the gate of hell discover Mazda?'

Shapur leant forward and closely scrutinized Ballista. 'And it is as Hormizd said: you have one or two of the marks of the Evil One on your face. It is certain that Mazda will not reveal himself to a man with freckles.'

Ballista fought down a suicidal urge to laugh.

'Now, to the question I must ask you,' said Shapur. 'Will you, of your own free will and following the custom of your people, swear a binding oath, a great and terrible oath, to carry out this task and, in success or failure, return to perform proskynesis before my throne?'

When Ballista and Cledonius gave their assent, Shapur commanded the things necessary for the ritual to be brought forth. The priests came forward carrying several bowls and two lambs. Ballista wondered what exactly was behind all this. What was Valerian thinking? It would be hard to find two Roman officers more detested by Macrianus the Lame. And what game was the King of Kings playing? Macrianus had betrayed Valerian to Shapur. He was hardly likely to want the old emperor freed and returned to power.

Hormizd handed a heavy knife and one of the lambs to Ballista. The young Persian explained in Greek the form the oath would take and said that Ballista would swear first. The northerner's heart sank at the weight of the words. An oath was an oath. But there was nothing else for it.

Crouching, Ballista pinned the lamb between his thighs. It bleated piteously. With one hand he gently pulled up its chin. With the dagger he cut some tufts from its head. He tossed the tufts in the air. They floated away in the quickening breeze. Lifting his arms to the sky, he began to speak.

'Zeus, be my witness first; the highest, the best of gods! Then the Earth, the Sun, and the Furies who stalk the world below to wreak revenge on the dead who break their oaths – I swear I will carry out my task in good faith. I will travel to Macrianus and spare no effort to arrange the ransom of Valerian, emperor of Rome. I swear, in success or failure, I will return to perform proskynesis before the throne of Shapur, the Mazda-beloved King of Aryans and non-Aryans.'

Again Ballista pulled up the lamb's head, roughly this time. He dragged the ruthless blade across its soft throat. The little lamb fell at his feet, dying, gasping away its life breath.

Ballista took a silver bowl in one of his bloodied hands. 'Zeus, god of greatness, god of glory, all you immortals.' He tipped out some of the wine. 'If I break my oath, spill my brains on the ground as this wine spills, my brains and the brains of my sons too.'

Calgacus and the others rode up to the walls of Zeugma late in the morning. It had all taken far longer than they had expected.

After the landslide, the Caledonian and the three cavalrymen had climbed down from where they had levered the rocks from the cliff. Demetrius and the other Dalmatian were where they had left them holding the horses. They had all mounted and waited.

Maximus had walked his horse up to them. The Hibernian was powdered white like a man who has worked a long day on the threshing floor. A cut showed bright red in the dust on his cheek. His face was motionless, drained. He had thanked them, haltingly, in a monotone.

Calgacus had seen the like before. A man who has resigned himself to death is unexpectedly saved but, instead of revelling in the reprieve from execution, in a released-from-gaol euphoria, the man is overcome by his troubles and fears, things he thought he had left behind him. Calgacus was not unduly perturbed. He knew that Maximus's moods changed like the weather in springtime. In no time the Hibernian would be his usual self.

Almost as soon as they set off, Calgacus had noticed a track leaving their path and running off to the left between a fold in the hills. Not long after, he saw another climbing the slope to the right. As the stars had paled and the sky lightened, track after track appeared.

The sun had risen as they came down from the hills, revealing a broad plain heavily worked by man. It was dotted with barns and farms and, here and there, hamlets, and even small villages. Although some of the buildings had been burned, it had not been done recently. Most showed signs of repair. In all probability, the destruction dated back to the previous Persian invasion, the so-called 'time of troubles', seven years earlier. Stretching away on either side of the path were thick groves of trees, mainly olives and pistachios, vineyards in leaf and corn standing tall even this early in the year.

Calgacus looked over at Maximus. The Hibernian's face still wore the blank thousand-pace stare of a man back from near-death in combat. If Maximus had not realized his stand may have been unnecessary, Calgacus was not going to tell him.

The horses were done in, so Calgacus had ordered the men to dismount. Leading their tired mounts, they had trudged across the plain. The last stage seemed to take for ever. In the distance, on the other side of the Euphrates, was the rounded mound of the citadel of Zeugma. The outlines of the city were clear in the bright spring air: the red roofs of the close-packed houses climbing the slopes, the sharp line of its wall, some type of tree dotted above and, on the very summit, the great temple and the palace. Gradually, they had been able to make out the details, but for a long time it seemed to come no nearer.

Finally, they were only half a mile or so from the city walls. They had reached the outskirts of the eastern necropolis. Calgacus gave the order to remount. They trotted past many types of tomb, bearing many gloomy images in stone. Among the heavily sculpted swags of flowers framing baskets of offerings to the dead and the eagles which the pious hoped would carry their souls to a better place, there were portraits. The men depicted stood, respectable in Hellenic cloak and tunic; the women sat demurely. Children clutched their toys. The paint was flaking from quite a few. Some of the tombs had been broken open and not resealed. Their doors gaped open, the interiors loomed black in the sunshine.

None of it depressed the spirits of the riders. They were almost at safety. The walls of the town were no further away than a goatherd could throw a stick. Calgacus flexed his wounded right arm. He had taken a sword cut in the final fight before they had escaped from the valley of tears. The wound hurt like a bastard. Still, here they were: safety in their grasp and the welcome hope of a fat reward from a grateful town councillor for returning his lost son. Calgacus glanced at the boy, who was fast asleep in the saddle in front of Demetrius. The Caledonian momentarily wondered how the family reunion had gone when the mother had returned without the child. Well, that was their concern. It would be an unfeeling sort of father who did not reward, and reward to the limit of his means or even beyond, a man who brought his son back from a fate that unmans one for ever, or maybe death itself.

Get hold of a decent reward, have a bath, a long sleep, clean clothes, then off for a drink and a girl. Maximus could always be relied on to sniff out the latter two. But their old companion Castricius, centurion of Legio IIII Scythica, was stationed at Zeugma. He had the inside knowledge. On the march out, he had taken them to a couple of places. The upmarket one on the Apamea side of the river had been horribly expensive. The other, the bar near the military base, had been fine.

Calgacus thought of Castricius in quite a fond way. The centurion had a thin little face, all lines and points, like that of a mythical creature dreamed up to entertain children with its mischievous tricks. But before he had joined the legions Castricius had been condemned to the mines – surely there was a law that stopped ex-slaves enlisting in the legions? – and he had survived. And not only that, he had lived through the fall of Arete. It would be a bad error to mistake Castricius for something harmless that entertained children.

'Virtus.' The challenge rang out from the walls. The gates were shut.

Calgacus moved his mount forward. He called up that they did not know the day's password – they were come straight from the field army north of Edessa.

'Identify yourselves,' shouted the guard.

'Marcus Clodius Calgacus.'

'Marcus Clodius Maximus.'

'Marcus Clodius Demetrius.'

Calgacus identified the boy – Antiochus, son of Barlaha, member of the Boule of Zeugma – and the four Dalmatian troopers gave their names, rank and unit.

'Wait there,' came the response.

As he waited, Calgacus thought of Marcus Clodius Ballista. When the Angle had given them their freedom, he had also, in legal terms, given them Roman citizenship. They, as custom prescribed, had taken both his praenomen and nomen as their own. For the rest of their lives, two-thirds of their names would bind the four men together.

Calgacus climbed down from the saddle. He pulled Pale Horse's ears, scratched its nose. Ballista loved the animal and, in an awful moment of clarity, Calgacus felt how much he loved Ballista. The Caledonian had been little more than a child himself when he had been taken as a slave north of the wall. A quick succession of owners – thank the gods his looks had forestalled any of them taking too close an interest in him – and he had found himself in Germania, in the hall of Isangrim, warleader of the Angles. Ballista had been just four when Isangrim had instructed Calgacus to serve as his son's manservant. Ballista had been a rather shy, sensitive child. Calgacus had watched Ballista as a youth trying to be brave on the training ground, in the hunting field and, eventually at the age of fifteen, in the battle line. Calgacus had been there on the dreadful day when the Roman centurion had ridden up and announced that the emperor Maximinus Thrax had demanded one of Isangrim's sons as a hostage. Of course there had been no question that Ballista's elder brother could go.

Calgacus had watched Ballista face down his misery. He had ridden at Ballista's side into the alien world of the Romans. On any reckoning, Ballista had done well in the service of the imperium. Yet Calgacus had always felt sorry for the young Angle, as surely torn from his people as the Caledonian himself. Whatever was thrown at him, Ballista tried to be brave. And now he was a captive of the Sassanids.

Calgacus buried his face in Pale Horse's flank. If all the miseries of the world had been set before him, it would not have touched him. He was already too full. Soundlessly, he mouthed some prayers to the half-forgotten gods of his childhood, to the gods he had never really believed in.

'Let them in.' The voice of the centurion broke into Calgacus's unhappiness. He straightened up.

The gates swung back. They led their horses in. Moorish auxiliaries, weapons drawn, swarthy faces mistrustful, ringed them. The gates slammed shut.

The centurion stepped down from the wall walk and appraised them closely.

'You are deserters.'

'No,' said Calgacus. 'Our patronus, the commander of these Dalmatians, ordered us to leave.' The Caledonian decided to take the initiative. 'If you could direct us to the house of the member of the Boule called Barlaha, we will return his son to him.'

'Oh no.' The centurion grinned. 'I can take care of that.'

Beside him, Calgacus felt Maximus stiffen. Calgacus put out a hand to restrain him.

The centurion gestured for the child to come to him. Unaware of the tension, the boy walked over to the officer. Reaching him, he turned and, in formal Attic Greek, thanked his rescuers. The centurion motioned a soldier to lead him away.

Calgacus was not ready to give up yet. 'We must see the governor Valens straightaway. Our patronus, Marcus Clodius Ballista, is an amicus of his, and we have much information about the Sassanids.'

'Oh, you will see the governor, but not the traitor Valens.' The centurion smiled unpleasantly. 'Valens fled to the west when ordered to report to Samosata. Given the emergency, Macrianus the Elder, as Comes Sacrarum Largitionum and the commander of what remains of Valerian's field army, has been forced temporarily to assume maius imperium over the whole East. Macrianus has appointed his amicus, the noble ex-consul Gaius Calpurnius Piso Frugi, to be governor of Syria Coele.'

Calgacus said nothing.

'I have no doubt that the new governor, Piso Frugi, will want to see you. Especially as I understand that your patronus, Marcus Clodius Ballista, led the emperor Valerian into a Persian trap and the barbarian has now justly been declared an enemy of the Roman people.'

The centurion smirked. 'Oh yes, the noble Piso Frugi will want to question you – although probably not until you have spent a few days in the cells under the palace.'

Calgacus remained silent.

'Now give up your weapons.' The centurion was thoroughly enjoying the moment.

Calgacus looked at Maximus and shook his head. Slowly, the Caledonian unsheathed first his sword then his dagger and threw them down in the dust at his feet. The others followed his lead.

At a signal from the centurion, soldiers came forward and efficiently searched the unarmed men. Calgacus winced as his wounded arm was wrenched. Their mounts, Pale Horse among them, were led away.

'All in all, a good morning's work,' the centurion said to his second-in-command.

'Just so, Dominus,' replied the optio. 'Three freedmen of a hostis arrested, four deserters apprehended and, to come, the gratitude of a member of the Boule whose son we will return.'

'Take them away.' The high country north of Edessa going up to the Euphrates and Samosata all looks much the same. But Ballista knew where he was as soon as he saw the lone pike standing stark on the horizon.

They had been riding hard all day. Two or three times, Persian patrols had closed to investigate. They had veered away, no explanation necessary, when they saw the golden ornaments on the bridle of the Sassanid officer's horse. No easterner in his right mind would interfere with a man going about the business of the King of Kings.

Now, the sun was low. Elongated shadows stretched out as they rode up to the crest. Tired and sore, Ballista composed himself in preparation for what he was about to see. It was not chance that the Sassanids had led them this way. Ballista halted his mount and looked up.

Turpio was just recognizable. Birds had pecked out his eyes; some of the flesh on his face was gone. Being impaled on the pike had prevented the scavengers of the earth reaching his head. What remained was barely corrupt. Although it seemed an age, it had only been five days. Ballista looked at his friend. Don't cry Over the happy dead But weep for those who dread To die.

The Persian officer broke into Ballista's thoughts. 'It was the will of Mazda.' Garshasp was also looking up at the grisly thing on the pike. 'I saw him die. Your friend died well.'

'He never lacked courage. Once, at Arete, he came this close' – Ballista snapped his fingers – 'to killing your king. As you say, the will of the gods.'

'When I was commanded to bring you this way,' Garshasp continued, 'I was told you were not to bury him. I am sorry.'

'Thank you. I would have done, even though the burial rites of Romans like him are not those of my people. We often burn our dead warriors.'

Garshasp grunted. 'Let us move on. It would be best to camp beyond the battlefield.'

Even in shadow, the valley of tears was a horrible sight. The tidal wave of war had swept its debris across its length. Everywhere were strewn discarded, hacked shields, bent and broken swords, the snapped shafts of arrows and, everywhere, the corpses of men and beasts. Here they lay in ones and twos. There, to the right, leading to the isolated hill rising from the floor of the valley, a thick carpet of them, where the Sassanid cavalry had broken Legio VI Gallicana. Another hideous pile on the slopes, where those too wounded to walk had been killed after the surrender.

The horses, unnerved by the scent of death, placed their hooves nervously amidst the carnage. A vulture, too gorged to fly, waddled off a bloated corpse. Some of the dead were more decayed than others. Ballista half remembered Turpio telling him it was all to do with climate and diet; damp westerners rot more quickly than desiccated men from the east.

They rode on after the sun had gone down. Garshasp was evidently as keen as the others to put some distance between them and the dead. Eventually, he called a halt.

Their new status as envoys had brought temporary eastern servants for Ballista and Cledonius. The two Roman officers sat on the ground and watched their horses being groomed and their tents erected. The sharp north wind made the latter tricky; sudden gusts flicked leather sheets aside, coiled guy ropes around limbs.

Cledonius sent away the youth who would have seen to Ballista's dressings. By the guttering torchlight, Cledonius did it himself. The ab Admissionibus had been kept by Valerian's side and had thus been spared some of the hardship of the march. Now, his long, thin face was close to the northerner; his hands worked deftly. They talked together softly in Latin.

'Ballista, it is – what? – over twenty years since you came into the imperium as a hostage for the good behaviour of your father's tribe – not that it has always curbed the inherent ferocity of you Angles. Anyway, you have spent more than half your life, not just in the imperium, but connected to the imperial court, and at times you are as naive as the day you emerged out of your damp northern forests.' Cledonius smiled affectionately. 'Of course Valerian knows that Macrianus loathes us – although I would say rather more you than me. I have never punched one of his sons in the balls.'

'So Valerian wants our embassy to fail?'

Cledonius shook his head in mock-wonder at Ballista's obtuseness. 'That is the general idea. Thanks to you, Valerian knows he was betrayed by Macrianus. But only a few know it. And those now within the imperium might find it hard to be believed. So Valerian has created a public spectacle where the lame one must break his oath to value the safety of the emperor above everything. At the very least, such despicable lack of loyalty and flagrant disregard of the gods will give a very poor start to Macrianus's campaign if he intends to elevate his odious sons to the throne. At best, it gives Gallienus in the west a just cause for war: revenge on the oath-breaker who betrayed his father, Valerian.'

Ballista thought for a moment. 'Why has Shapur agreed to the embassy?'

'Harder to say.' Cledonius shrugged. 'The King of Kings has not chosen to confide in me. But it seems he is equally well served by our success or failure.'

Now it was Ballista's turn to shrug. Immediately, he wished he had not. It hurt. 'Explain.'

Cledonius waited for a servant, who had come to tell them that their tents were ready, to move out of earshot. 'If, as expected, Macrianus rejects the demand to ransom Valerian, then Shapur has an excellent cause for the war to carry on. But on the other side of the coin, if, by some divine intervention, we get Macrianus to give up what is demanded, then Shapur gets a huge amount of gold and silver and certain other things which make his glory all the greater and, I feel sure, Mazda will guide him to another good and just reason for the fighting to continue.'

'Either way, we end up back on our bellies before the Sassanid throne.' Ballista sounded depressed. 'And then…'

'There is a lot of talk around Shapur of using the expertise of the Roman prisoners: building towns, dams, bridges, fortifications. As a trained siege engineer, you might end up doing that. It might not be too bad.'

Having agreed, in the most half-hearted way, Ballista said goodnight to Cledonius and went to his tent. The northerner was very tired.

It was long into the night, possibly around the end of the third watch, when Ballista woke with a feeling of profound dread. The wind had risen. He could hear nothing over its howling and snapping around the tent. It was not the noise that scared him, though, it was the smell: the thick, lanolin smell of waxed canvas.

Although he knew what he would see, a tiny part of Ballista hoped he was wrong. He forced himself to look. He was not mistaken. The faint glow of the torches outside illuminated the figure. It was standing, the tip of its hood touching the roof of the tent. As every time before, it was waiting.

Ballista got a double bridle on his fear. 'Speak,' he commanded.

The figure spoke, a deep, grating sound: 'I will see you again at Aquileia.'

'I will see you then,' Ballista replied.

The figure did not move. Under the hood, its eyes glittered. It hissed another word: 'Oath-breaker,' then turned and left.

Ballista did not call out for the guards. There was no point. On no previous occasion had anyone else seen the daemon of the emperor Maximinus Thrax.

Twenty-two years before, Ballista had sworn the military oath to Maximinus Thrax. By Jupiter Optimus Maximus and all the gods, I swear to carry out the emperor's commands, never desert the standards or shirk death, to value the safety of the emperor above everything. Ballista had not kept the sacramentum. Instead, at the siege of Aquileia, he had killed Maximinus Thrax, plunging a stylus into his throat. The other conspirators had beheaded the emperor, desecrated his body. Denying him burial, they had condemned his daemon to walk the earth for eternity.

Ballista had only told four people about the daemon: his wife Julia, bodyguard Maximus, body servant Calgacus and Turpio – and Turpio was dead. Julia, brought up by an Epicurean father, had tried to comfort her husband by rationalizing it. Maximinus only appeared when Ballista was tired, under great stress. It was just a figment of his overheated imagination. Ballista sniffed the air – waxed canvas. He did not think bad dreams left a smell.

It had been four years since the last apparition, the night Arete fell. Never before had the daemon said 'Oath-breaker'. He was a long way from Aquileia, but Ballista knew the daemon's words foretold something bad.

Demetrius sat on the hard-packed earth floor, his back against the rough stone wall. It was almost completely dark. There was just one tiny slit of a window, high up. It had admitted little light during the day and, when the sun went down, next to none.

After their arrest, the four Dalmatian troopers had been marched off straight away to the military cantonment. Ballista's three freedmen had been kept waiting at the gate until well past midday. When Maximus asked for food, the centurion had hit him hard across the back with his vine stick.

At long last, they had been ordered to their feet. Under heavy guard, they were led through the squared-off streets to the bridge over the Euphrates which gave the twin towns of Apamea on the eastern bank and Zeugma on the west a reason to exist.

At the bridgehead, the party had been brought to a halt. The approaches, narrowed anyway by bales of merchandise, were completely blocked by a mass of men, camels, mules and horses. Amid a fearful noise, the crush had surged up to the barrier, where a lone telones backed by some club-wielding members of the watch attempted to extract the custom dues rightly owed to both the imperium and the city. Demetrius wondered whether it had always been like that or if refugees from the east had made things worse.

When the Moorish auxiliaries laid about them, trying to force a way through, initially it had merely exacerbated the situation. Men had cursed, mules brayed, horses lashed out, and some camels had sunk to their knees, roaring. The centurion snapped an order. Swords were unsheathed. The men, if not the animals, in the crush scrambled to get out of the way.

Having told the telones and the civic watch to go fuck themselves, the soldiers had marched the prisoners across the pontoon bridge. The river was busy with boats and barges coming downstream from Samosata. Half a dozen big barges, piled high with produce, were moored, waiting for a gap to be opened in the pontoon so they could continue on south.

There had been another pause at a military checkpoint on the western bridgehead. It had been quieter there. The slop, slop sound of screws raising water from the river floated up. To one side, Demetrius noticed a massive iron chain coiled with vines and ivy growing through the unrusted links, the remains of the original bridge constructed by the god Dionysus on his way to the east to conquer India.

The formalities conducted, they moved on through what had until recently been a rich residential area. The majority of the houses showed signs of having been burnt. Only some had been repaired, and those hastily. After that, the land rising, they passed a theatre and crossed an agora, which brought them to the foot of the citadel. The path up was stepped and ran between dwellings that clung to the vertiginous slope. The tall terraced houses seemed to be built on top of each other and the path between them like the bottom of a ravine.

They entered through a gate in a low, rough wall and climbed on up through an orchard of fruit trees. At length, out of breath, they reached the summit. To their left was the great temple of the Tyche of Zeugma; a statue of the seated goddess could be glimpsed through the open doors. The guards turned them sharply to the right, towards the palace complex. From there they were taken to a side entrance, frogmarched down a flight of steps, along a corridor and unceremoniously pushed into a cell. The door slammed behind them, and they heard bolts being pushed home.

Demetrius had slumped to the floor. From there he watched Maximus and Calgacus carefully inspecting every inch of the gloomy, bare cell. They tried the door, stood on each other's shoulders to check the narrow window, tapped the walls, scraped at the floor. Eventually, frustrated, they hunkered down next to the young Greek. The older men talked in low voices. If they could get out, they would need horses, or they could try to make it to one of the barges waiting at the bridge, hide themselves among the produce, or maybe overpower the boatmen and take their place.

At some point in the afternoon, they heard the bolts drawn back, and the door swung open. Watchful guards covered them with drawn swords as a tray of food was put on the floor. The door was shut again.

There was some stale bread, a few handfuls of raisins and a big pitcher of water. Demetrius and Maximus fell on it. Calgacus used some of his share of the water to wash his wounded arm. When everything had gone, they were still hungry.

When the light faded, Maximus and Calgacus both fell fast asleep. There was no furniture, so they slept on the floor, their heads on their arms.

Demetrius could not sleep. It was not his hunger. Desperate though it was, the prison-stench of unwashed bodies, shit and fear took the edge off it, made him feel nauseous. He envied the calm, natural fatalism of his companions. Gods below, they had travelled so far, come through so much – and for it to come to this. Confined in this filthy cell – if he still lived, could Ballista himself be worse off? And the centurion had said that Ballista was now declared a hostis. Falsely accused of having led the old emperor Valerian into the trap that had cost his freedom, Demetrius's kyrios was now an outlaw to be killed on sight by any Roman citizen. The true traitor, that scheming bastard Macrianus the Lame, had seized the moment and was now the master of the eastern provinces of the imperium. Was there no such thing as divine justice? Did the gods even exist?

Demetrius lay down in the darkness. To steady himself, he turned to philosophy and the teachings of the Stoic masters. Everything that lies outside the inner man is an irrelevance. The things over which we have no choice – illness, bereavement, exile and imprisonment, death itself – all are irrelevant. Throw them aside. When enslaved, Diogenes was a free man. The King of Persia on his gilded throne may be a slave. Iron bars and stone walls cannot make a prison. A little comforted, he fell asleep.

A while later, a gentle pressure behind his left ear brought Demetrius awake. He jerked up. A hand clamped over his mouth. A faint light came from the open door. A figure stood there.

'Come.' The figure spoke in Greek with a heavy eastern accent. 'You come now.'

Maximus removed his hand.

'It could be a trap,' Demetrius whispered.

'Then we will swap one for another.' Maximus grinned.

The figure went in front of them along the corridor and up the steps. He stopped, looked about and led them out. Quickly and quietly, they moved through a maze of alleys until they emerged on the far side of the citadel to that through which they had come in.

The figure stopped again to look and listen, then waved them to follow him down into the orchard. The slope was steep, the soil underfoot crumbling and dry. Slithering and sliding, they went down, grabbing tree trunks to slow their momentum. The pale light of the young moon shone through the branches.

They came to a low wall. Demetrius realized that it must be the one that encircled the citadel. Without a word, the figure climbed it like a lizard. He dropped out of sight down the other side. Maximus and Calgacus followed, the latter protecting his wounded arm as he did so. Now that he was alone, a wave of panic threatened to overwhelm Demetrius. He started to climb. The wall was made of irregular stones. There was no mortar. Even so, Demetrius found it difficult. He grazed his knees, felt a fingernail tear. Lying on the top, he looked down. There was a drop, something over a man's height, on to the roof of the first of the terraced houses. Nervously, he swung himself over, hung for a moment and let go. He landed awkwardly. Hands steadied him.

The figure put a finger to his lips then gestured for them to follow. In single file, Calgacus, then Demetrius, Maximus bringing up the rear, they set off.

At first they went to the right. They were sheltered there, between the wall and the gentle pitch of the roof. Demetrius walked carefully, one hand on the wall, watching where he put his feet, afraid a tile would shift or give way.

They turned left into a ridged dip where the roofs of two houses came together. At the end was another drop, a bit deeper this time. One by one, they turned round, lay down flat, pushed their legs out, wriggled backwards, hung by their hands for a second and let go. The landing site was the apex of a roof.

The figure indicated they were again to go to the right. Demetrius felt his heart shrink. The pitch of this roof was steeper, and it ran down to the black, square opening of an atrium. Slip here, and there was nothing to stop you sliding all the way down, over the edge and out into emptiness; a fall of two storeys to a shattering impact on a concrete impluvium. Demetrius imagined his smashed body lying there, his blood staining black the waters of the shallow raintank.

Their mysterious guide climbed down, fingers hooked into the gutter at the top, legs spread wide, and edged crabwise along the horrible slope. Calgacus followed. Demetrius stared at the gutter. It looked so fragile: his existence would hang by an insubstantial piece of fired clay.

'No choice, boy,' Maximus whispered in his ear. 'Don't look down.'

Fumbling, clumsy with fear, Demetrius lowered himself. He could feel the heat of the day's sun still in the tiles under his body. Tentatively, he began to edge along. Athene, Artemis, all the gods hold your hands over me. Inch by inch he crept. Great Zeus, Hermes, protector of travellers. His palms were slick with sweat. He crept further. Fear sent little spasms of cramp running through his limbs. His breath was coming fast and shallow. He looked over his shoulder. The tiles went on and on, sickeningly steep, dropping into yawning black nothingness. His muscles locked. He could not move.

Demetrius felt Maximus grip his right wrist, Calgacus his left. The mere touch of the other men made the young Greek feel a little calmer.

'We will guide you,' Calgacus said in his ear. 'One hand at a time. Mine first.'

Demetrius felt the increased pressure on his left wrist. Reluctantly but obediently, he unclenched his fingers and let Calgacus move his hand along. He grasped the next length of guttering. Maximus repeated the procedure with the other hand.

Only once did Demetrius look to his left. The roof stretched away into the distance. A wave of panic rose in him. He fought it down. He kept his eyes on the tiles under his nose. Hand by hand, Maximus and Calgacus helped him along.

Demetrius became aware that Calgacus was shifting his position. A moment later, his boot struck the roof that extended out to form the next side of the atrium. A jerky scramble and the Greek boy was on the ridge, legs either side, in no danger of a fall for the time being.

On the far side of the ridge, a gentler slope ran down to a low wall. They slithered down. Past this was a drop to a stepped lane. No matter, they were safe where they were. In the shelter of the wall, they paused to get their breath back. Somewhere, not far away, a baby was crying. It had not struck Demetrius that the noise they were making could wake those sleeping in the houses below. At any moment, they might raise the alarm. Suddenly, he was eager to be moving again.

Calgacus touched Demetrius's arm. They were off once more, crouching below the level of the parapet wall, using their hands, scurrying like monkeys. This uncomfortable but unthreatening way of moving lasted all too short a time. The wall on the right and the roof on the left were at an end. Demetrius was unhappy to see Calgacus get down on all fours. The Caledonian crawled out on to a free-standing wall.

Great Athene of the Aegis, I can do this, thought Demetrius. On one side, there was a drop to the stepped street, on the other an equally awful fall to a paved courtyard. I can do this. Grey-eyed Athene, I can.

Demetrius inched out. The top of the wall was a couple of feet across. No reason to fall. Just keep going. No earthly reason to fall.

He was concentrating so hard on keeping his balance that he almost bumped into Calgacus. The Caledonian had stopped and was manoeuvring himself to lie down full length. Not knowing why, Demetrius did the same.

The noise came from behind. The Greek boy peered anxiously over his right shoulder and down. Two watchmen were walking down the street. They carried lanterns, and each had a club over his shoulder. As they drew nearer, Demetrius could hear one of them talking.

'So the tribune says, "So, Centurion, is that how the men use the camel?" And the centurion says, "No, Tribune, they use it to ride to the nearest brothel."'

The other watchman laughed briefly. 'That joke was old when Cronos was young,' he said. When he was level with Demetrius, he stopped. He held up his lantern and shone it into a small courtyard on the other side of the street. He went in and carefully looked all around a fountain in the middle. Gods below, he was far too diligent.

The watchmen moved on. The humourist started up again. 'Do you know the one about the donkey and the murderess?'

'Yes,' replied the other unencouragingly.

Giving the impression that such rebuffs were not uncommon, his companion stopped and put his lantern down on a step. He retied his laces. Retrieving the lantern, he stood up and walked on. Then, without warning, he stopped again. He turned to look back the way they had come. Then he looked up.

'Thieves! There up on the wall!'

Calgacus was up, running fast. Without time for thought, Demetrius was doing the same.

The slope of the roof loomed in front. Scrambling up it, boots slipping on the tiles, Demetrius glanced down. The first watchman had a bell in his hand. Demetrius saw him pull out the straw which held the clapper in place. Its clanging echoed across the sleeping city.

Their unintroduced guide led the fugitives on. The pitch of the roofs here was gentle. Up and down they went, vaulting over ridges. Fear gave wings to Demetrius's feet. Below, the watchmen were chasing. Somewhere in front, another bell was ringing.

'Alley ahead. No problem to jump.' In the stress, the guide's eastern accent had dropped away.

Demetrius saw Calgacus leap the divide. Demetrius found himself mouthing one of Ballista's sayings – Do not think, just act.

As soon as he took off, the young Greek knew he had mistimed it. Arms flailing, he was dropping too fast. His stomach thumped into the edge of the roof, knocking the wind out of him. He was slipping back. His fingers clasped the corner of a tile. It came loose. He was slipping faster, legs thrashing in the void. Far below, the tile shattered.

Demetrius clung to the final row of tiles. They began to shift. A hand gripped his wrist. Calgacus's face was contorted with effort; Demetrius's weight was dragging the old Caledonian with him.

'Let go,' Demetrius screamed.

Slowly sliding to his doom, Calgacus hung on. Sweat was pouring down his ugly old face.

Another hand grasped Demetrius's other wrist.

'One, two, three, pull!' Together, the guide and Calgacus managed to haul Demetrius up a little.

'One, two, three, pull!' Demetrius's chest was over the lip of the roof. He clawed himself fully over. His saviours yanked him further up. Calgacus was doubled up, holding his injured arm. Maximus landed like a cat behind them.

'This way, quick!' The guide was off again.

Below, the streets and alleys echoed with shouts and the ringing of bells. Here and there shutters were thrown back, light spilling out.

They raced around the opening of an atrium and across an unbroken span of roofs. Temporarily, they were out of sight from the ground.

'Down there.' The guide pointed. 'Stay there until I come back.'

One by one, they dropped into a dark space formed by four converging slopes. The guide's face appeared above them. 'Do not move,' he said. Then he was gone.

A few moments later, there was a cacophony of yells. Demetrius could not resist peeping out. The guide had gone back the way they had come and was now standing over an alley, gazing this way and that, a picture of uncertainty. Then, as if spurred by the shouts from below, he set off. Moving fast, he passed the hiding place and ran off to the south. The sounds of pursuit followed him. With one hand, he swung up over a wall and was gone from sight.

Slumping back down, Demetrius saw that Maximus was tearing strips from the sleeve of his tunic and binding Calgacus's arm. The old Caledonian's eyes were screwed shut. Dark blood was running from his wound.

'Thank you,' Demetrius whispered.

Calgacus opened his eyes. 'Think nothing of it.'

They waited. The sounds of the chase faded. Immobile, they grew cold.

Demetrius wondered what they would do if the guide did not return. Was the underworld like this? Cold, powerless, an eternity of unfulfilled waiting? One thing was certain: they could not stay here for long. They had to eat soon or else become too weak to flee. Demetrius could not stop shivering.

There was a slight scraping sound and the guide was back. 'Good exercise, yes?' His thick eastern accent had returned. 'Now, you follow. Is easy now.'

True to his word, the rest of the rooftop journey consisted of straightforward stages. Only one passage gave Demetrius concern. A beam jutting out from beneath the eaves held two leaning buildings apart. As he wriggled across, Demetrius looked down. An intricate pattern of washing lines ran across the alley. They would do nothing to slow a falling man. The young Greek kept his eyes on the wood in front of him.

At long last, they reached the lowest level of houses. Via an outhouse, they dropped to the ground. Across the street was the inner side of the main city wall. At no great interval, the torches of sentries could be seen up on the walkway. The guide pressed them back into the shadow of the outbuilding. He hissed for them to wait. Calmly, he walked out into the open and around the corner.

This time, the guide returned more quickly. Wasting no words, he indicated that they should follow. He took them towards one of the towers. On the battlements, the torches illuminated a standard bearing the eagle, lion and Capricorn of Legio IIII Scythica. Fortunately, the sentries were all on the other side. Under the tower, low in the wall, was a small postern gate. It was unlocked. The guide led them through and pulled it shut behind them.

Keeping close to the wall, they moved south. Every time a sentry paced above their heads, they froze. Out in the night, a fox barked. They followed the wall as it curved round to the east. Before long, the low, gloomy structures that indicated a necropolis emerged from the darkness on their right. With a wave of his hand, the guide led them away from the wall into the city of the dead. Like ghosts, they flitted between the tombs. He stopped before one that had been cut into the living rock. The door opened easily. Once inside, he closed the door and pulled a curtain across its frame.

Sparks flashed as the guide worked a flint on a steel. He lit a small clay lamp. Their shadows danced grotesquely on the walls. Demetrius looked around. A table and three couches stood in the centre of a large room cut from the rock itself. On the wall opposite the door were relief sculptures of eagles, wicker baskets, swags of flowers. In the other two walls were arched recesses; inside them long, low piles of broken roof tiles. The air was still, with a strong odour of mould and decay.

'You wait here. Your friend will come.' The guide's eastern tones were now thick to the point of parody. 'I go now. You wait.' He indicated for Maximus to shield the lamp and slipped behind the curtain. They heard the door open and close again. They were alone in the house of the dead.

Exhausted, Demetrius sat on one of the couches. With a wince, Calgacus sat beside him. Maximus put the lamp on the table and busied himself. First, he checked for any food that may have been left behind from a funeral feast. There was none. Then he started sorting through one of the mounds of tiles in one of the recesses. He came across with three shards, handily shaped and razor-sharp.

Demetrius gazed at the recess from which Maximus had emerged. In rooting about, he had disturbed the tiles. A hand stuck out from the wall now, yellow-black with decomposition. How could people use these places for sexual assignations, thought Demetrius. He could understand a low-class prostitute maybe, with no place of her own to go. You often saw them hanging around the tombs outside city walls. But others – free men and women? It was unthinkable. No wonder that, in the famous story, the shade of Philinnion left her tomb to visit her lover in her old house.

Maximus pointed to the curtain and the door behind it. In his most serious tone, he said, 'Sure, but you have to ask, just who the fuck was he?'

'No idea,' said Calgacus. 'But he could climb the shite out of a wall, just like a monkey.'

'Do you remember,' said Maximus, 'when we were in Arete, there was a woman that fucked a monkey?'

Demetrius found himself laughing with the others. 'I think you will find,' he said, 'it was just a woman who gave birth to a child that looked like a monkey.'

'And how did that happen?' Maximus sounded indignant, before adding thoughtfully, 'Unless of course she happened to look at a monkey just at the moment love reached its true, destined end.'

A sound from outside stopped their laughter. Men with horses. Several of them, reining in by the door; dismounting.

Quick as lightning, Maximus and Calgacus were either side of the curtain, the shards of tile to the ready. Maximus blew out the lamp. Unsure what to do, Demetrius rose from the couch. Feeling foolish, he adopted an approximation of the fighting crouch of the others.

There was the sound of the door being opened. The curtain moved slightly as the night air caught it. Demetrius held his breath.

'I am a friend.' The voice from beyond the curtain was pitched low, the Latin words muffled. 'I am coming in alone. Do not attack.'

The curtain was drawn back. Pale moonlight flooded into the tomb. In the opening was the black silhouette of a man. He stepped over the threshold and stopped, his eyes taking their time to adjust. He did not flinch as Maximus noiselessly put the shard to his throat.

'Welcome back from the dead, boys.' As he spoke, the man turned to look at Maximus and the moonlight fell on his face – a strange-looking face, all lines and points.

'Castricius, you little bastard!' Maximus hugged him. Calgacus slapped him on the back. Demetrius shook his hand. The centurion's palm was gritty.

'Shite, I hoped our saviour would turn out to be the eupatrid whose son we rescued.' Calgacus shook his head in what seemed genuine sorrow. 'He would have given us a fine reward.'

'And if it had to be you, Castricius,' Maximus joined in, 'there was no need to leave us there so long.'

'And it's lovely to see you too,' said Castricius. 'You are lucky I'm here at all. I only got back tonight from a tour overseeing the quarries up the road at Arulis. Nasty, dirty, dangerous work – by Silvanus, the legionaries hate it – very tiring. I thought about getting a good night's sleep, maybe rescuing you tomorrow.'

'Certain, I imagine the new governor thinks your life history fits you for the quarries.' Maximus was grinning.

'Quite possibly – Piso is a cunt.' The centurion's voice changed. 'I was very sorry to hear Ballista was taken.'

'He will get back,' said Calgacus. 'Always does.'

'I do not doubt it.' Centurion Castricius became businesslike. 'The last watch of the night is almost over. There are three horses outside, tacked up, weapons to hand, food and water in the saddlebags, even a little money. Which way will you go?'

'Do you think it unwise just to ride down the main road west – Regia and Hagioupolis to Antioch?' Calgacus asked.

Castricius considered for a time. 'Piso will be annoyed you have escaped. Of course, you three are of no importance, and Piso is naturally indolent. But he is desperate to appear competent in the eyes of his Macrianus the Lame. He might be so keen to suck his dominus's cock that he will send a troop of horses down the obvious route.'

'I have a friend in Hierapolis – well, a man I met on the journey out…' Demetrius's words trailed off.

'There is no direct road,' said Castricius. 'It must be about forty miles as the crow flies, tough going, but it still might be best to go south.'

Outside, a legionary was holding the horses. In turn, the fugitives thanked Castricius and mounted up.

'One thing,' said Maximus. 'Who was the easterner who led us over the roofs?'

The small centurion laughed. 'That was no local. One of my boys from Legio IIII – a scaenicus legionis. If you had to talk your way out of something, I thought it would be useful to have an actor to help you.'

As they rode away, Demetrius reflected on life's absurdities. Most legions, especially those stationed out in the east, contained a troupe of soldier-actors. It helped pass the time. A scaenicus legionis had appeared to save them like the deus ex machina he must have so often played.

Ballista was standing in the governor's palace in Samosata. He was watching the Sassanid envoy trying to control himself. Garshasp the Lion might have first won his cognomen in some battle in the east, but presumably it had stuck because it suited him. Unusually for a Persian, his hair had a reddish tinge. Long and thick, it invited comparison with a mane. When angry, as he certainly was now, his eyes flashed.

They had been in Samosata for nine days. Finally granted an audience with Macrianus the Lame, they had been left waiting in the basilica for over an hour. If you thought the Sassanid King of Kings the equal of a Roman emperor, the twin eyes of the world, the two lamps in the darkness of mankind, as Ballista had heard Garshasp put it, this was a studied insult.

Ballista himself had relished the delay. Every night that passed took him further away from the nocturnal apparition of the daemon of Maximinus Thrax. Ballista needed recourse to his familiar mantra – the daemon cannot physically harm you, avoid Aquileia and all will be well – less and less frequently There were other reasons Ballista welcomed the delay. Every day in Roman territory was a day he did not have to return to Sassanid captivity. Here in Samosata he could indulge the fantasy that all he had to do to be reunited with Julia and the boys was call for a horse and set out on the road to Antioch. And he wanted to be far away from the memory of the cell in Carrhae. Rolled face down, limbs stretched out, tunic hauled up; Allfather, that had been close. The assault had shaken the northerner more than he cared to admit.

To break the run of his thoughts, he looked around the basilica. The last time he had been here, there had been plague. It was long gone, but the ends of some of the swags of laurel – their scent considered a preventative of disease – had not been removed. The floor was unswept. If one were planning a coup, as Ballista was convinced Macrianus was, such incidentals might well be overlooked. Valerian's imperial throne had gone from the dais at the end of the long room. Instead, six seats adorned with ivory stood in a row – the curule chairs symbolic of high Roman magistracies.

The doors swung open. A herald announced Marcus Fulvius Macrianus, Comes Sacrarum Largitionum, Praefectus Annonae, holder of maius imperium in the Oriens. The titles rang out sonorous and impressive: the treasurer of the whole empire, its supply-master, with overriding military authority in its eastern territories.

Click, drag, step. Macrianus advanced down the aisle. Click went his walking stick, his lame foot dragged, and his sound one took a step. He was followed by two more youthful versions of himself. His sons had the same long, straight nose, receding chin and pouchy eyes, but Quietus and Macrianus the Younger walked easily, with a confident swagger.

Behind the family came three more men. All had deserted the setting sun of Valerian in time to rise high in the newly emerging regime. There was the elderly nobilis Pomponius Bassus, recently appointed governor of Cappadocia, the senator Maeonius Astyanax, as ever clutching a papyrus roll as evidence of his intellectuality, and, most sinister of all, Censorinus, commander of the frumentarii. Emperors came and went, but there was always a feared Princeps Peregrinorum like Censorinus in charge of the imperial secret service.

On the dais, Macrianus handed his stick to one of his sons. He pulled a fold of his toga over his head and poured a libation of wine. Raising his hands to the heavens, he said a prayer to the immortal gods of Rome. His tone was imbued with the fervour of true belief. This was a man who had caused untold suffering to his fellow citizens with his persecution of Christians. Few could be more dangerous, more inhumane than an active and shrewd politician guided by burning religious certainty.

Once everyone was settled in their seats, Macrianus the Lame indicated that the embassy should begin.

Garshasp spoke briefly. Avoiding Greek, the diplomatic language of the east, he used his native tongue. Having captured Valerian in battle, Shapur, King of Kings, would now accept a ransom for him. Cledonius and Ballista had been brought here to arrange it. Knowing Persian, Ballista noted that the interpreter filled out the phrases to make them less brusque.

Cledonius took the floor. Having served for many years as ab Admissionibus to Valerian, he was well versed in courtly etiquette. His speech was full and round in its Latin orotundity. He moved seamlessly between high-flown sentiments and hard details.

The words slid off Ballista's mind like rain off a tiled roof. No one expected this embassy to succeed; not Shapur or Valerian, and none of the men in this room. Macrianus the Lame had exercised great ingenuity and foresight in order to betray Valerian to the Persians. The very last thing he would want was the return of the aged emperor. Instead, as Quietus had told Ballista in a moment of fury, Macrianus intended that his sons take the purple. Cledonius's speech ran on. As the historian Tacitus had revealed long ago, the rule of the emperors had created a gulf between words and reality.

Suddenly, with a flourish, Cledonius produced a document from his toga. He began to read. It was a letter from Valerian to his loyal servant Macrianus. It was a direct order to the Count of the Sacred Largess to leave Samosata and come to the emperor in Carrhae.

In the silence that followed Cledonius's rhetorical device, Macrianus rose to his feet. He came to the edge of the dais and leant on his stick.

'Is anyone so insane that he would willingly become a slave and prisoner of war instead of being a free man?' Macrianus shook his head, as if overcome by the folly of it all. 'Furthermore, those who are ordering me to go from here are not my masters. One of them, Shapur, is an enemy. The other, Valerian, is not master of himself, and thus can in no way be our master.'

It was in the open. Macrianus had publicly denied that Valerian was emperor any longer. Although Ballista knew the devious Count of the Sacred Largess had been working towards this for at least a year, he still felt vaguely shocked. The northerner looked around to see how everyone else was taking it. Up on the dais, all heads except one nodded in solemn agreement. Quietus was smiling in exultation. Again, through the main body of the basilica, there seemed much muted approval. Ballista noted that the audience contained a significant percentage of those high-ranked senators who had followed Valerian to the east.

Macrianus pointed to Garshasp. 'You will return to your master tomorrow morning.'

When the translator had finished, the Sassanid warrior turned and, without a word, left the room.

Macrianus gestured with his walking stick. Its silver head of Alexander the Great flashed. 'Cledonius and Ballista, you will remain here to serve the Res Publica.'

Cledonius spoke up clearly. 'I will not.' His thin face was a mask. 'I am bound by the sacramentum I took to Valerian Augustus and by a specific oath to return to Shapur.'

'And you, Ballista?' Macrianus betrayed no emotion.

'The same.'

The lame man leant on his stick, thinking. 'The sacramentum is a personal oath to an emperor,' he said at length. 'When a man ceases to be emperor – he dies or is taken prisoner – the oath ceases. Any oath you made to Shapur was under duress and so is invalid. The gods of Rome would want you to remain and give your service to the imperium.'

'Sophistry,' said Cledonius. 'No emperor has ever been held captive by barbarians before. Who is to say Valerian is no longer emperor? In any event, there was no duress when I gave my oath to Shapur. I will return.'

Macrianus pointed at Ballista.

Temptation caressed Ballista. One word. Just one word, and he was safe with his family. Back with Julia. Back with his sons; looking into their huge blue eyes, burying his face in their long hair, inhaling the smell of them.

No – Ballista tried to push temptation away. It clung like a whore on a Massilia dockside. Think of Julia, Isangrim, Dernhelm. No – there would be no safety. The very opposite. One word would bring down the terrible curse in the oath he had sworn to Shapur. If it were just on his own head, he could take it. But not on his sons'. If I break my oath, spill my brains on the ground as this wine spills, my brains and the brains of my sons too.

'I return with Cledonius to the emperor.'

'So be it.' Macrianus's face was impossible to read. He tapped his stick for quiet, declared the consilium over, intoned another heartfelt prayer and made his way out. Click, drag, step. His supporters jostled as they were forced to keep to his slow pace. Click, drag, step.

Outside, Maeonius Astyanax was waiting. 'Ballista, a word,' he said.

The senator led Ballista round the basilica to a south-facing garden which abutted on to the palace. The path was flanked by statues of Greek intellectuals, arranged alphabetically: A was Aristotle, B, Bion. They stopped by Homer.

'Your wife and sons are well in Antioch.'

'Thank you.' Ballista felt a hollowness in his chest.

Astyanax fiddled with the book roll in his hands and looked up at the marble bust of Homer. He was going to say more.

Ballista waited. He had spoken to Astyanax a few times. But, beyond the senator's fervent support for Macrianus the Lame, Ballista knew little about him. Julia had once said that rumours linking the two men all involved disgusting impropriety.

Ballista realized he had never really looked at Astyanax before. He was a middle-aged man, with short hair and a short, full beard. His lips were soft and fleshy; his forehead intensely wrinkled. Astyanax twisted the papyrus between his fingers. The man was nervous.

Astyanax looked away from the marble face of the blind poet. His gaze traversed the wall of the palace, as if seeking something to distract him in the diamond-pattern limestone blocks.

At last, glancing at Ballista, then looking away, he began to talk. 'Macrianus genuinely believes he has the mandate of the gods to restore the Res Publica.'

'I do not doubt it.' Ballista's voice was neutral.

'The Christians have to die. Their open denial of the gods, their disgusting atheism, turns the immortals against the imperium.'

'Quite possibly.'

Astyanax turned and looked Ballista in the eye. 'Valerian had to go. He was old, weak, irresolute. The gods demand a strong hand at the helm.'

Ballista said nothing.

'In this age of iron and rust, we must have an emperor.' There was a wheedling quality to the senator's voice.

'We have one: Gallienus. And a Caesar in his son Saloninus,' Ballista replied.

Astyanax shook his head. 'They are far away on the northern frontier.'

'One of them could travel east.'

Astyanax's fleshy lips twitched. 'They are beset by your barbarian cousins.'

Ballista ignored the gibe. 'Gallienus has a brother and another son in Rome. One of them could assume the purple.'

'Gallienus is a degenerate. There is no reason to think his close relatives any better.'

'Certainly Gallienus likes to drink and he likes to fuck.' Ballista nodded at the papyrus in the other's hands. 'He writes poetry and listens to philosophers too. But I have campaigned with him. He knows how to fight.'

Astyanax dismissed the argument with a wave of his hand. 'Macrianus has all the virtues necessary in a princeps. He has self-control, piety, courage, intelligence, far-sightedness.'

'And a crippled leg.' Ballista spoke more harshly than he had intended. 'No man can ascend the throne of the Caesars with a physical deformity.'

'True.' Astyanax smiled. 'That is why Quietus and Macrianus the Younger must take the throne. The sons will be guided by their father.' The treason voiced, Astyanax hurried on. 'The majority of the senate will be with us. They hate Gallienus – his lack of dignitas, the way he excludes them from military commands, panders to the common soldiers, promotes illiterate barbarians.'

Ballista was silent for a moment. There was more than some truth in it. 'A senatorial majority does not win a civil war, armies do,' he remarked.

'Quite so. Those who matter in the east – those who hold the armed provinces – are already with us. While you were away, the governor of Cappadocia met an unfortunate end. Exiguus was killed by bandits.' Astyanax raised his eyebrows. 'Latrones everywhere – dangerous times. Cappadocia is now held for Macrianus by Pomponius Bassus.'

When Ballista did not react, Astyanax carried on. 'Strangely, when he heard the news, Valens, the governor of Syria Coele, fled to the west. He has been replaced by Piso Frugi, another close amicus of the Count of the Sacred Largess. Achaeus, governor of Palestine, is with us. A devout persecutor of Christians, he is aware what the times call for. The prefect of Egypt, Aemilianus, is an ambitious man, and the governor of Syria Phoenice, Cornicula, a weak one. They both realize where their advantage lies. Doubtless, the isolated governors of Osrhoene and Arabia will fall into line.'

Astyanax spread his hands wide in a studied oratorical gesture. 'Then there is Sampsigeramus, the king of Emesa. Seven years ago, in the time of troubles, he put a myriad horsemen in the field. The god he serves has told him to pledge his support. As I said, we command all the armed might of the east.'

Ballista laughed. 'Then why do you need me?'

'We are not sure we do. Yet you might be useful. Much of Valerian's field army was drawn from the west. You have served there. They might like a general they know.' Astyanax sighed. 'And, corrupted by Gallienus, they might prefer a general of your origins.' There was a wealth of contempt in the last word.

'Then it is unfortunate for you that I am oath-bound to return to Shapur.'

Astyanax turned a bland face to the northerner. 'Macrianus dealt with that in the consilium. Anyway, you do not have a reputation for being over-pious. Under you, the persecution of Christians in Ephesus ground to a halt. Your wife's family are Epicureans. Like them, you may think the gods are uninterested in humanity.'

At the mention of Julia, the hollowness in Ballista returned.

Now Astyanax looked pained, his forehead even more wrinkled. 'After Valerian was captured, you were declared a hostis, an outlaw to be killed on sight. That order has not yet been rescinded.' He paused. Ballista feared where this was going.

Astyanax resumed, in short, measured sentences. 'Your family is in Antioch, the capital of the province of Syria Coele. The new governor is on his way there from Zeugma. Piso Frugi is a zealous supporter of Macrianus. Some might say overzealous. The wife and children of a hostis, a traitor to the Res Publica, a traitor to Macrianus – things might not go well for them.'

Ballista could not speak.

Astyanax patted his arm. 'Never take a hasty decision. Sleep on it.' Dawn came up over the stirring city of Samosata. As every day at this time, the beams were removed and the Edessa gate was swung open. Since the capture of Valerian, the guards had exercised great vigilance. When they were satisfied there were no Sassanids lurking, they waved the telones to carry on. The customs official stood back as Ballista and Cledonius led the horses through the gate.

Outside, the two men moved off the road to wait for Garshasp. Ballista did not want to talk. He studied the motley throng of refugees. Day by day, more arrived from south of the river. Ballista wondered how many of them were Persian infiltrators. It was an obvious move. Certainly, Shapur would have thought of it. Yet the telones seemed to be doing nothing but searching them for taxable goods. Perhaps it had not occurred to Macrianus.

Ballista could sense Cledonius's growing impatience to talk. The northerner turned his back and looked at the defences of Samosata. On the other side of the ditch, the wall was tall and thick. Although its facade was a diamond pattern of small blocks, it was smooth enough. But here and there were buttresses. Were they ornamental or did they indicate structural weakness? Either way, they were a bad thing, providing a modicum of cover for attackers. And the town wall was long. It would take an enormous number of men to defend it. Up on its hill, the citadel might be daunting, but the town itself would be difficult to hold.

The horse Ballista was holding tossed its head. He soothed it, bringing his face close to its nostrils, letting it inhale his breath. The automatic gestures did not break Ballista's line of thought. Did Macrianus even intend to try and hold the town? What were the lame one's plans?

Astyanax had outlined the plot in the most favourable light. Yet in some ways it was what he had not said that was most important. Astyanax had not mentioned any western governors as supporters. Presumably, there were none. And he had not talked of the governors of the so-called unarmed provinces of the east. While they commanded no legions, there were small detached troops of soldiers in every province. As well as these stationarii, there would be some whole units of auxiliary cavalry and infantry. It seemed that the governors of Asia, Lycia-Pamphylia, Cilicia and the other unarmed eastern provinces had not fallen in behind Macrianus either.

Astyanax had admitted that Virius Lupus, with his one legion in Arabia, and Aurelius Dasius, with the remnants of two in Osrhoene, had yet to commit. His ambiguity concerning the allegiance of Cornicula in Syria Phoenice and Aemilianus in Egypt was also telling. Two more eastern legions not yet secured.

Yet most important of all was what Astyanax had not said about the client rulers. He had made much of the adherence of Sampsigeramus of Emesa but had said nothing about Odenathus, the Lord of Palmyra. In the time of troubles, Odenathus had raised thirty thousand warriors, horse and foot. Ballista had commanded Palmyrenes: Cohors XX Palmyrenorum at Arete and Equites Tertii Catafractarii Palmirenorum at Circesium. They were fine fighters, deadly with a bow, fearsome hand to hand. The oasis city of Palmyra, Tadmor to its inhabitants, lay between Rome and Persia. Now its lord, Odenathus, the Lion of the Sun, held the balance in the east.

Garshasp, his devotions complete, the risen sun worshipped, walked out of Samosata. He shook Ballista's hand. Ballista passed him the reins and gave him a leg-up. The Persian waited.

Cledonius embraced Ballista.

'Are you sure?' There was no accusation in the voice of the ab Admissionibus.

'Yes.' Ballista made as if to say more.

'There is no need to explain,' said Cledonius. 'My wife is dead, my son with Gallienus.'

Ballista nodded. He helped Cledonius into the saddle. 'We are playthings of the gods,' said the ab Admissionibus. 'They give us harsh choices.'

The two mounted men turned and rode slowly away towards the bridge south. Ballista watched them go.

The words of his oath tormented Ballista: If I break my oath, spill my brains on the ground as this wine spills, my brains and the brains of my sons too. Julia put the papyrus roll down on the desk with the others. She pinched the bridge of her nose between forefinger and thumb. It was hot, even in the shaded part of the atrium. She had chosen this house for their family dwelling in Antioch because the Epiphania district caught whatever breeze there was. This morning, there was none.

She tapped the stylus against her teeth. The deeds of the property just outside Daphne were straightforward enough, but the other was more complicated. Ever since the charcoal burner had died, intestate, two of his relatives had disputed ownership. If Julia wanted the property, there seemed nothing for it but to pay off both. She was not sure why she was so determined to buy it. Certainly you could build a wonderful summer retreat there, high on the southern slopes of Mount Silpius, magnificent views but tucked away, almost impossible to find. Had she not been brought up in a household of the strictest Epicurean philosophy – the gods are far away and have no interest in humanity – she might have thought a deity had put the idea in her mind. Four years earlier, Ballista had narrowly survived an attempt on his life there. Possibly she wanted to buy it as a sort of offering for the return of her absent husband. If so, her philosophical rationality was slipping. Her late father, the stern senator Gaius Julius Volcatius Gallicanus, would not have approved.

Julia signalled for Anthia, the maid attending her, to bring a drink. At least Julia was not one of those Roman women of the old Res Publica whose husbands only kissed them to smell if there was wine on their breath. And she was not one of those Greek women still to be found in some cities whose menfolk made them wear the veil in public and locked them in their rooms at night.

Anthia brought the drink, mixing the water and wine as the domina liked it. Julia thanked her and sent her away. Sipping the cool liquid, she reflected that it was still a man's world. She would have to get her tutor to approve her purchases. Luckily, it was a formality. He was one of her many cousins, far away in Gaul and far more concerned with his fish ponds than anything else. She was lucky too in her husband. Ballista had never had much interest in their domestic arrangements. As soon as they were married, he had handed the household keys and the cura of their home to her.

Julia smiled to find herself playing with the iron ring on the third finger of her left hand. When Ballista had given it to her at their betrothal party, she had not loved him. Far from it. Her mother, may the earth lie lightly on her, had been opposed to the match, but her father had talked her round. Julia had dutifully done what her father wished. Although her family was still able to prove the senatorial property qualification, many of their ancestral estates had been confiscated more than half a century before by Septimius Severus, as a result of the family's unwise support for his rival Albinus. Their influence had not recovered. Marcus Clodius Ballista may have been born a barbarian but, nine years ago, he had held equestrian status in Rome, and – her father's winning argument – he had been a close amicus of the then reigning emperor Gallus.

If, as Epicurus taught, the ultimate aim of human life was freedom from disturbance, Julia wondered why people got married. Ataraxia and marriage did not seem obvious companions. It was not as if Ballista had many more faults than most husbands. To the usual insensitivity, stubbornness, drunkenness and outbursts of violent temper, he added only an ineradicable barbarian naivety. No, it was none of these that unsettled her freedom from disturbance. Since she had come to love him, it was his absences on campaign. One day, he would not return. Julia thought of their sons. Their beautiful, innocent sons. She would never, like the Spartan women of old, tell them to return with their shield or on it.

As Julia picked up her writing block, her new steward appeared. Before he could announce them, three shabby-looking men followed him out into the shade on the far side of the atrium. Julia had time for just a flash of annoyance before she recognized them. Dropping the writing things, she ran around the pool. Dignitas forgotten, she threw her arms around the neck of the ugly old man at the front.

'Calgacus.' She kissed him on both cheeks.

'Steady, Domina. The servants will talk,' said Maximus. She kissed him too, then turned and embraced Demetrius.

'How did you get here? We had heard nothing.'

Their smiles faded. The three men looked embarrassed. 'We travelled by night, avoiding people. A… a friend of Demetrius hid us for a time in Hierapolis. Before that, Castricius got us out of a problem in Zeugma.' Calgacus stopped. He fiddled with the sling on his arm.

'It was as if the underworld had swallowed you.' Julia clapped her hands. 'Now you are back – the gods be praised. Let me look at you. Calgacus, you are injured.'

'It is nothing.' The elderly Caledonian waved his good hand indecisively. 'Domina, your husband…' His voice trailed away.

Maximus also tried to speak and failed.

'Domina' – Demetrius took a deep breath and let the words out in a rush – 'your husband is a prisoner of the Sassanids. He ordered us to leave him. There was nothing we could do. I am sorry.'

Julia tipped her head back and laughed. The three men exchanged looks. Women were fragile, their grip on reality weak. Had the news unhinged her?

Wiping her eyes, she shook her head. 'The news has outrun you.' She raised herself on tiptoe and kissed Demetrius on the forehead. 'He is free, back with the Roman field army in Samosata. He has been appointed Prefect of Cavalry.' She laughed again. 'Not only is my husband free, Ballista is now officially a Vir Perfectissimus.'