Half turning, Pacorus noticed his reaction and smiled. ‘Mithras is mighty indeed,’ he said. ‘And I will know if you are lying.’

Tarquinius met his stare. ‘You will not be displeased,’ he said quietly.

Pacorus restrained himself from saying more. Originally, he had been awed by Tarquinius’ ability to anticipate the future, and to pluck the solutions to overwhelming problems from thin air. Although he would not openly admit it, the Forgotten Legion’s initial successes in driving out the marauding tribes had almost exclusively been thanks to the haruspex. But some months ago, Tarquinius’ accurate predictions had dried up, to be replaced with vague, generalised comments. At first Pacorus had been unconcerned, but this had soon changed. He needed the prophecies because his position as commander of Parthia’s eastern border was a double-edged sword. While a huge promotion from his previous rank, it came laden with expectation. Pacorus relied on divine help just to survive.

Attacks by war bands from neighbouring lands had been frequent for some time. The reason for this was simple. In anticipation of Crassus’ invasion, all local garrisons had been emptied more than twelve months previously. King Orodes, the Parthian ruler, had diverted every available man to the west, leaving the frontier region with few defences. The nomadic tribes had quickly seized the opportunity to rape and pillage every settlement within easy reach of the border. Growing bold on the back of success, soon they were vying to carve up Margiana.

Pacorus’ mission from Orodes was simple: to smash all opposition and restore the peace. Fast. This he had done. But his very success jeopardised his position: the king was wary of any officer who became too effective. Even General Surena, the leader who had achieved the stunning victory at Carrhae, had not been safe. Nervous of Surena’s new-found popularity, Orodes had ordered his execution not long after the battle. The news kept officers such as Pacorus in constant uncertainty: eager to please, unsure how to proceed – and desperate for aid from sources such as Tarquinius.

Fear is my last psychological advantage over Pacorus, thought the haruspex. Even that had worn thin. Weariness filled him. If the god revealed nothing, he would have to come up with something believable, enough to convince the ruthless Parthian not to kill them all. But after months of stringing Pacorus along, Tarquinius doubted his imagination was capable of any more.

They walked in silence along a passageway constructed in the same way as the staircase. At length, it opened out into a long, narrow chamber.

Pacorus moved left and right, lighting oil lamps which sat in small alcoves.

As light flooded the room, Tarquinius took in the paintings on the walls, the low seats on each side and the heavy wooden posts supporting the low roof. Inevitably though, his eyes were drawn to the end of the Mithraeum, where a trio of altars was positioned below the dramatic, brightly painted image of a cloaked figure in a Phrygian cap crouched over a kneeling bull while plunging a knife deep into the beast’s chest. Mithras. Stars glittered from his dark green cloak; a mysterious figure bearing a flaming torch stood witness on each side of him.

‘The tauroctony,’ whispered Pacorus, bending his head reverently. ‘By killing the sacred bull, Mithras gave life to the world.’

Behind him, Tarquinius sensed the guard bowing. He did the same.

Slowly Pacorus led the way to the altars. Muttering a brief prayer, he bent from the waist. ‘The god is present,’ he said, stepping aside. ‘Let us hope he reveals something to you.’

Tarquinius closed his eyes and gathered his strength. Unusually, his palms were sweaty. Never had there been an occasion where he needed help more. He had made momentous predictions before now, many of them, but not under the threat of immediate execution. And in here, there was no wind, no cloud, no flocks of birds to observe, not even an animal to sacrifice. I am alone, the haruspex thought. Instinctively, he knelt. Great Mithras, help me!

He looked up at the godly figure depicted above him. There was a knowing expression in its hooded eyes. What can you offer me? it seemed to say. Other than himself, Tarquinius had no answer. I will be your faithful servant.

He waited for a long time.

Nothing.

‘Well?’ demanded Pacorus harshly, his voice echoing in the confined space.

Desolation swamped Tarquinius. His mind was a complete blank.

Furious, Pacorus uttered a few words to his guard, who stepped in close.

This is it, Tarquinius thought angrily. Olenus was wrong in thinking I would journey back from Margiana. Instead, I am to die alone, in a Mithraeum. Romulus and Brennus will be slain too. My whole life has been wasted.

And then, from nowhere, an image seared his retinas.

Nearly a hundred armed men creeping in on a score of Parthian warriors sitting around a fire. Tarquinius’ skin crawled. Talking among themselves, the Parthians were totally unaware.

‘Danger,’ he blurted, jumping up. ‘There is great danger approaching.’

The guard paused, his knife still ready for use.

‘From where?’ demanded Pacorus. ‘Sogdia? Bactria?’

‘You don’t understand,’ cried the haruspex. ‘Here! Now!’

Pacorus’ eyebrows rose disbelievingly.

‘We must warn the others,’ urged Tarquinius. ‘Return to the fort, before it’s too late.’

‘It’s night-time, in midwinter,’ scoffed Pacorus. ‘Twenty of the finest men in Parthia are on watch outside. So are your friends. And nine thousand of my soldiers are only a mile away. What possible danger can there be?’

His guard leered.

‘They are about to be attacked,’ answered Tarquinius simply. ‘Soon.’

‘What? This is how you cover up your incompetence?’ shouted Pacorus, his colour rising. ‘You’re a damn liar!’

Instead of denying the accusation, Tarquinius closed his eyes and brought back the image he had just seen. Somehow he did not allow panic to take hold. I need more, great Mithras.

‘Finish it,’ Pacorus ordered.

Tarquinius could sense the knife approaching, but he remained still. This was the ultimate test of his divining ability. There was nothing else he could do, no more he could ask of the god. Cool air brushed Tarquinius’ neck as the guard’s arm rose high. He thought of his innocent friends above. Forgive me.

Carrying down the tunnel, the unmistakable sound of a man shouting the alarm reached their ears.

Shock filled Pacorus’ face, but he regained control fast. ‘Treacherous dog. Told your friends to cry out after a certain time, eh?’

Tarquinius shook his head in silent denial.

There was a long pause before the air filled with blood-curdling yells. Far more noise than two men could make.

Pacorus blanched. He hesitated for a moment, then turned and ran from the chamber, his guard close on his heels.

Rising, Tarquinius was about to follow, when he felt a surge of power.

The god’s revelation was not over.

But his friends were in mortal danger.

Guilt mixed with anger, and desire for knowledge. He knelt again. There was time.

A little time.

A long half-hour passed. The temperature, which had been hovering just below freezing all day, fell much further. Using a stockpile of timber left there for the purpose, the Parthian warriors fed the blazing fire until it was the height of a man. While a few stood guard on a perimeter roughly thirty paces out, the remainder hunched around it, talking between themselves. Few even glanced at Romulus and Brennus, the interlopers.

The two friends stamped up and down, doing their best to keep warm. It was a futile battle. Still they felt no inclination to join the Parthians, whose attitude towards them was at best contemptuous. Brennus fell into a deep reverie about his future while Romulus studied the jackal, hoping to understand its reasons for staying. His efforts were in vain. Finally the animal stood up, shook itself in a leisurely manner and trotted off to the south. It was lost to sight instantly.