‘And Figulus and Gallus had few friends,’ Romulus added.

‘Not thousands!’ The Gaul gave a short, sarcastic laugh.

And so it went on. Romulus’ prayers to Mithras grew ever more frantic, but their situation did not change. The days stretched into a week, and the pair grew haggard and irritable. There was one occasion when Novius and his friends attempted to jump them in the alleyway outside the barracks, but Romulus’ quick knife throw stopped the attack in its tracks. Caius’ left thigh was now heavily bandaged, and the veterans’ relentless hounding slackened somewhat. But the respite would merely be temporary. They would not be able to keep up their guard for ever.

Both were therefore relieved when, one frosty morning, Vahram ordered two centuries – theirs and another – out on patrol. For a few days, there had been no news from one of the legion’s outposts that were positioned east of the main camp. The seven fortlets, each with a garrison of a half-century and a handful of Parthian warriors with horses, had been built in strategic positions overlooking various approach routes into Margiana from the north and east. High mountains protected the south and south-east. There was usually little news from the small forts, but twice a week riders were sent back regardless. Whatever their faults, Pacorus and Vahram kept themselves well informed of everything going on in the area. The need for this had been bloodily reinforced by the attack at the Mithraeum.

Romulus’ and Brennus’ feelings were not echoed by their comrades as they prepared for the patrol. Loud curses filled the warm, close air as yokes were dug out of the tiny storerooms behind the sleeping space for each contubernium. Their destination was only twenty miles away, but Roman soldiers always travelled prepared. Besides, Vahram had ordered rations for four days. The yokes, long, forked pieces of wood, carried everything from a cooking pot and spare equipment to sleeping blankets. Along with his armour and heavy scutum, they brought the weight carried by each man to over sixty pounds.

‘This is bloody pointless,’ Gordianus grumbled, lifting another legionary’s mail shirt over his head so he could put it on. ‘A fool’s errand.’

‘We’ll meet the messenger halfway there,’ said the man he was helping. ‘And watch the prick piss himself with laughter as he watches us walk back.’

There were vociferous mutters of agreement. Who wanted to leave the safety and warmth of the fort for no reason? It was probably all down to a couple of lame horses.

‘I don’t know,’ said a familiar voice. ‘A lot of things can happen on patrol.’

Romulus looked up to find Novius standing in the doorway. Behind him were their other main tormentors, Caius and Optatus.

Automatically the young soldier’s hand reached for his gladius; Brennus did likewise.

‘Relax.’ Novius’ smile was evil. ‘There’ll be plenty of time for that later.’

Romulus had had enough. Lifting his sword, he stood up and moved towards the little legionary. ‘I’ll gut you now,’ he swore.

Novius laughed and was gone, followed by his comrades.

‘Gods above,’ said Romulus wearily. ‘I can’t take this much longer.’

Brennus’ red-rimmed eyes told him the same story.

At first, little was said by anyone the next morning. It was cold and miserable, and marching while carrying full kit was not easy. While the men were well able for the task, it was necessary to get into a good rhythm. Inevitably, Gordianus began to sing. Smiles broke out as the tune was recognised, a familiar ditty involving a sex-starved legionary and every whore in a large brothel. There were endless verses and a bawdy chorus to roar at the end of each. The soldiers were happy to join in: it passed the time, which often dragged on such patrols.

Normally Romulus enjoyed singing the refrain, with its countless sexual positions and innuendos. Today, though, he was gloomily imagining what might happen during the patrol. If they encountered any trouble, Novius could use the opportunity to strike. In the midst of a pitched battle, it was all too easy to stab a man in the back without anyone noticing.

Brennus’ nudge darkened his mood even further. They had reached a crossroads five miles from the fort; the Gaul was pointing at a crucifix that stood on a small mound to one side. Pacorus had ordered it positioned so that all who passed would see it. Like those outside the front gates, the cross had just two purposes: to slowly kill condemned men, and to give graphic warning of the punishments at Parthia’s disposal.

The crucifixes were rarely empty. Falling asleep on duty, disobeying an order or angering Pacorus: all were common reasons for legionaries to die on the simple wooden structures. Even Parthian warriors who incurred his wrath were sometimes executed in this manner.

Gordianus’ voice died away, his song unfinished.

Romulus closed his eyes, trying not to imagine himself and Brennus ending their lives in such a way. With Pacorus’ life hanging in the balance, it was still a distinct possibility – if Novius and his lot didn’t do the job first.

Despite the early hour, there were carrion birds clustered all around the crucifix: on the ground, on the horizontal crossbar, even on the lifeless shoulders of their prey. Bare-headed vultures pecked irritably at each other while ravens darted in opportunistically to take what they could. Overhead, the huge wingspans of eagles could be seen, gliding serenely in anticipation of a good meal.

By now, everyone’s gaze was on the frozen corpse that sagged forward, its head hanging. Thick ropes were tied around the dead man’s arms and long iron nails pierced his feet. Everyone knew him: it was a young legionary from Ishkan’s cohort who had been caught stealing bread from the ovens two days before. Dragged on to the intervallum before the whole legion, he had first been beaten with flails until his tunic was shredded and his back a red, bleeding ruin. Then, naked except for a loincloth, the wretch was forced to carry his cross from the fort to the lonely crossroads. Ten men from every cohort had accompanied him as witnesses. By the time they had reached the desolate spot, his torn, bare feet were blue with cold. This was not enough to dull the pain of the sharp nails being driven through them.

Romulus vividly remembered the man’s thin, cracked screams.

Around him, the other legionaries’ faces were full of dull resentment – except those of Novius and his friends, who were laughing behind cupped hands.

Darius, their stout senior centurion, sensed the bad feeling and urged his men to march faster. They needed little encouragement. As the soldiers came alongside, the nearest vultures lifted their bloated bodies into the air with lazy wing beats. Others further away just waddled out of reach. In the depths of winter, food was hard to come by, and the birds were reluctant to leave this ready feast. There would be no let-up until a skeleton hung from the cross.

Romulus could not tear his gaze away from the frozen body. The only part to remain inviolate was its groin, covered by the loincloth. Empty eye sockets stared into nothingness; peck marks covered its cheeks, chest and arms. Its mouth was open in a last, silent rictus of pain and terror. Half-torn-off strips of flesh hung uneaten from its thighs, where the largest muscles were. Even its feet had been chewed, probably by a resourceful jackal standing on its hind legs. Had the man been alive when the vultures first landed? Felt the sensation of breaking bone as powerful jaws closed on his frozen toes?

It was revolting, but compelling.

Romulus blinked.

Beneath the horror, there was more.

Over the previous weeks, there had been time to study the air currents and the cloud formations over the fort. Romulus had become meticulous, noting every bird and animal, observing the pattern of snowfall and the way ice formed on the river that flowed past the fort. Having watched Tarquinius, he knew that literally everything could be important, could provide some information. It frustrated him immensely that little seemed to make sense. But by following the haruspex’ instructions, predicting the weather had at last became simple enough. Of course this was of interest but Romulus wanted to know far more than when the next storm would strike. Annoyingly, though, he had seen nothing about Tarquinius, Pacorus or Novius and the other veterans. Nothing useful.