Later, Romulus would remember the timing with awe.

‘Gods above,’ muttered Brennus, his teeth chattering. ‘I hope Tarquinius is done soon. Otherwise we’re going to have to join those bastards by the fire.’

‘He won’t be long,’ Romulus replied confidently. ‘Pacorus has reached the end of his tether with him.’

Everyone in the Forgotten Legion knew that when their commander lost his temper, men were executed.

‘The prick’s been looking twitchy,’ agreed Brennus, counting the Parthians for the umpteenth time. There are too many of them, he decided. ‘Probably order us all killed next. Shame the jackal didn’t stick around to help, eh?’

Romulus was about to reply when his gaze fell on the two furthest sentries. Wraithlike figures had appeared behind them, bearing long knives. He watched disbelievingly for a heartbeat before opening his mouth to shout a warning. But it was too late. The Parthians toppled backwards and out of sight, silent sprays of red jetting from their cut throats.

None of their companions noticed.

‘To arms!’ Romulus roared. ‘We are under attack from the east!’

Alarmed, the other warriors scrambled to their feet, reaching for their weapons and staring out into the pitch darkness.

From it, fearsome yells rose into the freezing air.

Brennus was beside Romulus in an instant. ‘Wait,’ he cautioned. ‘Don’t move yet.’

‘They’re spotlit by the fire,’ said Romulus, understanding.

‘Fools,’ muttered Brennus.

The first arrows descended as they watched. Fired from beyond the firelight, they fell in a dense, deadly rain. A perfectly laid ambush, it was bizarrely beautiful to watch. More than half the Parthians were killed outright by the volley, and several others were wounded. The remainder frantically grabbed their bows and loosed shaft after blind shaft in response.

Romulus raised his silk-covered scutum and was about to race forward, but Brennus’ great paw stopped him again. ‘Tarquinius . . .’ he protested.

‘Is safe underground for the moment.’

Romulus relaxed a fraction.

‘They’ll charge next,’ the Gaul said as the terrifying shouts increased in volume. ‘And when they do, let’s give them a little surprise of our own.’

Brennus’ guess was correct. What he had not foreseen was the number of attackers.

There was another shower of arrows and then the enemy came in at a run. Dozens of them. With bows like those of the Parthians slung over their shoulders, they waved swords, knives and vicious-looking short-headed axes. Dressed in felt hats, ornate scale mail and knee-high boots, the brown-skinned men could only be one nationality: Scythian. Romulus and Brennus had already encountered the fierce nomads in skirmishes on the border. Although their empire’s heyday had passed, the Scythians still made unrelenting enemies. And their hooked arrow heads were coated in a deadly poison called scythicon. Anyone even scratched with it died in agonising pain.

Brennus cursed quietly, and Romulus’ stomach clenched.

Tarquinius was still in the Mithraeum, and they could not just leave him to his fate. Yet if they tried to rescue the haruspex, certain death would come to all of them. There were at least fifty Scythians visible now, and more were appearing. Bitterness filled Romulus at the randomness of life. The idea of returning to Rome now seemed laughable.

‘They can’t have missed the noise,’ Brennus whispered. ‘Pacorus is no coward. He’ll come charging out at any moment. And there’s only one way to save their lives.’

‘Go in, quick and silent,’ said Romulus.

Pleased, Brennus nodded. ‘Hit any Scythians by the temple’s entrance. Grab Tarquinius and the others. Then make a run for it.’

Clinging to his words, Romulus led the way.

They ran hard and fast, their cold muscles aching with the effort. Thankfully, adrenalin soon kicked in, giving them extra speed. Javelins in hand, both cocked their right arms back, preparing to throw when the time was right. Engrossed with the surviving Parthians, the Scythians were not even looking outwards. They had encircled their foes, and were closing in.

With a century behind us, thought Romulus wistfully, we’d smash them into pieces. Now though, they had to trust that Tarquinius emerged at the right time and they could escape into the night. It was a slim hope.

Like two avenging ghosts, they closed in on the Mithraeum’s unguarded entrance.

Still they were not seen.

Cries of fear filled the air as the last Parthians realised that their fate was sealed.

A few steps from the hole, Romulus was beginning to think that they might just do it. Then a lightly built Scythian straightened up from a prone Parthian, wiping his sword on the corpse’s clothing. His mouth opened and closed as he saw them. Snapping out an order, the Scythian rushed forward. Nine men followed, some quickly sheathing their weapons and unslinging their bows.

‘You look for Tarquinius,’ yelled Romulus as they skidded to a stop by the opening. ‘I’ll hold them.’

Trusting his friend implicitly, Brennus dropped his pila by Romulus’ feet. Ripping a torch from the ground, he clattered down the steps. ‘Won’t be long,’ he yelled.

‘I’ll be dead if you are.’ Grimly, Romulus closed one eye and took aim. With the ease of long practice, he threw his first pilum in a low, curving arc. It hit the lead Scythian twenty paces away, skewering right through his scale mail and running deep into his chest. He dropped like a pole-axed mule.

But his comrades scarcely paused.

Romulus’ second javelin punched into a stocky Scythian’s belly, taking him out of the equation. His third missed, but the fourth pierced the throat of a warrior with a long black beard. Giving him a little more respect now, three Scythians slowed down and strung shafts to their bows. The four others redoubled their speed.

Seven of the whoresons, Romulus thought, his heart pounding with a combination of madness and fear. Poison arrows too. Bad news. What should I do? Suddenly, Cotta, his trainer in the ludus, came to mind. If all else fails, take the battle to an unsuspecting enemy. The element of surprise is invaluable. He could think of nothing else, and there was still no sign of Brennus or Tarquinius.

Yelling at the top of his voice, Romulus charged forward.

The Scythians smiled at his recklessness. Here was another fool to kill.

Reaching the first, Romulus used the one-two method of punching with his metal shield boss and following with a thrust of his gladius. It worked well. Spinning away from his falling enemy, he heard an arrow strike his scutum. Then another. Thankfully, the silk did its job and neither penetrated. A third whistled past his ear. Knowing he had a moment before more were loosed, Romulus peered over the iron rim. Two Scythians were almost on him. The last was a few steps behind, while the trio with bows were fitting their second shafts.

Romulus’ mouth felt bone dry.

Then a familiar battle cry filled his ears.

The Scythians faltered; Romulus risked a glance over his shoulder. Springing from the entrance like a great bear, Brennus had launched himself half a dozen steps forward.

Next came Pacorus, screaming with rage. He was followed closely by the hulking guard, waving his knife over his head.

There was no sign of Tarquinius.

Romulus had no time to dwell on this. He spun back and barely managed to parry a powerful blow from a Scythian. He stabbed forward in response, but missed. Then the man’s comrade nearly took off his sword arm with a huge downward cut. It missed by a whisker. Sparks went flying upward as the iron blade struck the flagstones, and Romulus moved fast. The second Scythian had overextended himself with the daring blow, and in the process, exposed his neck. Leaning forward, Romulus shoved his gladius into the unprotected spot between the man’s felt hat and his mail. Slicing through skin and muscle, it entered the chest cavity, severing most of the major blood vessels. The Scythian was a corpse before Romulus even tried to withdraw his blade. Shocked, his comrade still had the presence of mind to lower his right shoulder and drive forward into Romulus’ left side.