Romulus saw the haruspex watching the blaze and took hope.

Great Mithras, Tarquinius prayed reverently. Although this wounded man is my enemy, he is your disciple. Grant me the ability to save him. Without your help, he will surely die.

Felix and Brennus laid the unconscious Parthian on to his bed.

The remaining servant gaped as Tarquinius drew his dagger.

His response provoked a chuckle. ‘As if I’d kill him now.’ The haruspex leaned over and began slicing open Pacorus’ blood-soaked clothing, leaving the wooden shafts in place. A few moments later, the Parthian was as naked as the day he was born. His normally brown skin had gone a grey, unhealthy-looking colour, and it was hard to see the shallow movements of his chest.

Romulus closed his eyes at their commander’s horrifying injuries. Around each, the flesh had already turned bright red – the first sign that the scythicon was having an effect. But the worst area was his chest wound. It was a miracle that Pacorus had not been killed outright by the arrow, which had punched between two ribs to lie very close to the heart.

‘That means death,’ said Brennus quietly.

Tarquinius lifted his eyebrows, silently contemplating his task.

Felix sucked in a long, slow breath. ‘Why did you bother carrying him back?’

‘He has to survive,’ answered Tarquinius. ‘If he doesn’t, we’re all dead men.’

His trust in the haruspex absolute, Brennus waited. This was the man who had known – incredibly – what his druid had predicted, before his whole tribe had been massacred.

But the little Gaul looked worried.

Romulus knew how he felt. Yet Tarquinius was right. The extremely cold weather meant that any long journeys were far too dangerous without proper supplies. They had had little choice but to return here. Now their fates rested with the nearly dead man lying before them. Or rather, in Tarquinius’ ability to save him. Looking at Pacorus’ injuries, it seemed an impossible peak to climb. Automatically, Romulus’ gaze flickered to the statue on the altar. Mithras, we need your help!

It was then that a group of excited, upset servants arrived, led by the peasant who had fled on their arrival. Bearing blankets, linen sheets and steaming bronze bowls of water, they laid down their loads near the bed. At once they were urged from the room by Romulus. Only the two original men remained, to hold up more lamps by the bed, in turn providing the haruspex with light. Moments later a guard arrived, carrying Tarquinius’ medicine bag. He blanched at Pacorus’ appearance. Muttering a prayer, he backed away hastily and took up a position by the door.

Delving into the pack, Tarquinius produced a set of iron surgical instruments, a selection of which he dropped into the scalding liquid. The remainder were placed neatly alongside in case they were needed. There were scalpels, forceps and hooks. Strange-looking probes and spatulas lay beside different types of saws. A roll of brown, fibrous stitching material appeared, made from the outer lining of sheep’s gut. Trimmed off, dried and then stretched into tough thread, it could be used to hold together most tissues using round-bodied or triangular cutting needles. Romulus had seen the haruspex use many of the metal tools before, operating on the injuries of soldiers with great success. Although skilful in their own right, the legion’s few surviving surgeons had been amazed.

Beneath Tarquinius’ healing hands, men who would normally have died had not. Torn arteries were tied off, preventing death through blood loss. Tendons were carefully repaired, restoring function to useless limbs and toes. After the scalp had been lifted, even a man’s skull could be sawn open to allow the removal of a blood clot on the brain’s surface. According to Tarquinius, the keys to success were an expert knowledge of anatomy, and absolute cleanliness. Such surgery fascinated Romulus and he moved closer to watch. This challenge would surely test his friend’s abilities to the limit. Compared to the relatively clean wounds inflicted by the razor-sharp blades of spears and gladii, those made by the arrows were ragged and contaminated with scythicon.

Pacorus was already halfway to Hades.

Fully aware of the mountainous task facing him, Tarquinius looked at the figure on the altar and bent his head, once. Mithras, help me once more!

The significance of the gesture was not lost on Romulus.

Felix’ face changed as Tarquinius prepared to begin. ‘Time to get warm,’ the little Gaul muttered, sitting down by the fire with a sigh. Few men chose to witness such gory work.

Romulus and Brennus did not move.

‘Hold his arms,’ said Tarquinius briskly. ‘He might wake up. This really stings.’ Pulling the cork stopper from a small flask with his teeth, he poured some strong-smelling liquid on to a piece of clean cloth.

‘Acetum?’ asked Romulus.

Tarquinius inclined his head. ‘Vinegar is excellent at preventing blood poisoning.’

They watched him gently clean the wounds; Pacorus did not even stir.

The haruspex tackled Pacorus’ arm first. Slicing either side of the wooden shaft, he used a metal probe to free the barbed arrow head. Any bleeding was stopped with special clamps and then tied off with gut. Following this, the muscles were closed in layers. Pacorus’ leg was treated similarly. It was the chest wound that took the most effort, however. Gripping special retractors, Tarquinius pried apart two ribs to allow withdrawal of the arrow. Closing this wound was an urgent process, he explained. If too much air leaked into Pacorus’ chest cavity he would die. As Romulus watched, his understanding grew. Keen to learn more, he questioned Tarquinius closely about his techniques.

‘You should have seen enough by now,’ the haruspex pronounced with a sigh. ‘The next test will be for you to operate on an injured soldier.’

Romulus flinched at the prospect. To dress a wound in the midst of combat was one thing, but this was another.

‘There’ll be plenty of casualties in the future,’ said Tarquinius shrewdly. ‘I can never treat them all.’

Romulus nodded in acknowledgement. It was brutal but true. As Romulus had witnessed himself, the haruspex treated only those whom he had a chance of saving. Very seriously wounded legionaries were often left to die. If they were lucky, they received a draught of mandrake or the painkilling papaverum to help them on their way, but most died screaming in agony. Any attempt to save their lives by him, however inexperienced, would be better than the lingering hell they currently endured. Determination filled Romulus to soak up all the medical information he could.

At last the prolonged surgery finished. Muttering under his breath, Tarquinius produced a tiny bag, allowing a faint dusting of powder from it to fall over the Parthian’s wounds. The falling particles smelt strong and musty.

‘I haven’t seen you use that before,’ commented Romulus curiously.

‘Some call it mantar,’ the haruspex answered, tying up the pouch. ‘Few even know of it; I’ve only come across it once, in Egypt.’ He weighed the bag carefully in his hand. It looked as light as a feather. ‘This cost me three talents.’

‘How much was there?’ asked Romulus.

Tarquinius looked amused. ‘When I bought it? About three small spoonfuls.’

They all stared at him with amazement. That amount of gold would let a man live comfortably for the rest of his life.

Tarquinius was in a talkative mood. ‘It’s excellent at killing infection.’ The pouch disappeared inside his tunic again.

‘Even that caused by scythicon?’ Romulus could not conceal the strain in his voice.

‘We will see,’ answered Tarquinius, eyeing the figure of Mithras. ‘I’ve saved a man’s life with it before.’

‘Where does it come from?’