Heads lifted at the prospect of survival and Brennus let out a great sigh. His journey was not over.

'Can we trust him?' asked Felix.

'We haven't a chance in Hades waiting here,' said Bassius grimly. 'Break testudo! Form up in two files!'

The soldiers lowered their shields with trepidation, fully expecting a volley of arrows to be loosed.

Nothing happened.

Impassive bearded faces surrounded the twenty survivors of three thousand. Silently the riders nearest the Roman legions pulled apart, opening an avenue wide enough for men to pass through two abreast.

It seemed too good to be true.

'Follow me, boys! Nice and slowly,' announced the centurion calmly. 'We can't let the bastards think we 're scared.' Bassius moved off between the ranks of archers, his head held high. Despite his wound and the crushing defeat, the veteran's spirit burned undimmed, and his men followed gladly. Romulus could have sworn some of the warriors inclined their heads with respect as the ragged mercenaries passed, their scuta and javelins held in the marching position.

They had to tramp over the fallen to get by and every soldier following Bassius knew what their fate would be. But with Parthian horsemen watching from a few feet away, there was nothing they could do.

When the injured realised that some of their comrades were escaping, desperate calls for help rang out. 'Help me up,' cried one, his left leg pinned to the ground by an arrow. 'I can make it back.'

Romulus' heart filled with pity. It was one of the men from their century. Before he could move out of rank, Brennus' huge fist grabbed him.

'He's one of ours!'

'Don't even think about it!' the Gaul hissed. 'They'll gut you like a fish.'

'We are the only ones who stood our ground,' agreed Tarquinius.

Romulus watched the nearest warriors. One gave him a wolfish grin as he slid easily from the saddle, a long curved dagger in his hand.

Staring helplessly at the approaching Parthian, the mercenary panicked. 'Don't leave me here!'

'You don't even know his name,' said Tarquinius. 'Will you try and save the rest of them too?'

'He ran, leaving us to die,' growled Brennus. 'Coward.'

Romulus hardened his heart with difficulty. 'May the gods give you swift passage.'

'No!' screamed the injured soldier. 'Don't ki . . .' There was an abrupt silence, replaced by a soft spraying noise.

Romulus turned back.

The man's throat had been cut. His expression was startled as both carotid arteries showered the sand in a crimson fountain. Toppling slowly to one side, the mercenary's body twitched a few times and lay still.

Cries of fear rang out as the remainder realised what was about to happen. Yet it was only what they would have done to enemy survivors in the same circumstances.

'Eyes to the front!' roared Bassius. 'They are all dead men.'

Romulus did his best to ignore what they were leaving behind. The Parthians moved amongst the fallen like wraiths, killing without mercy, silencing the screams. Only Bassius and his twenty men were being allowed to go free.

'We have survived one great danger,' said Tarquinius reassuringly.

Romulus shook his head, forcing himself to believe. What else was there to hold on to?

The walk back to the Roman lines seemed to take forever. But not a single arrow followed the tiny remnant of the mercenary cohort. Surena had been true to his word. Unlike Crassus, who had flouted a peace treaty in his quest for fame and riches.

As they drew nearer, it was obvious that the army had finally been marshalled into one continuous front.

Romulus nudged Tarquinius. 'The general has read your mind.'

'Too late,' replied the Etruscan. 'The cataphracts will charge soon. One thousand of them.'

Romulus shuddered. Could anything be more terrible than what he had just witnessed? Brennus saw the young man faltering. 'The gods must be protecting us,' he said bluffly. 'We 're still here!' The Gaul's mind was still spinning at being alive. But only through divine intervention could they have survived the lunacy of that charge.

Just twenty to thirty paces had been left between cohorts now, allowing each to manoeuvre without leaving space for the Parthians to utilise the gaps. Crassus had placed a huge number of centurions in the front ranks. He knew it was imperative that the legions withstand the next attack and was relying on the seasoned officers' ability to hold the soldiers steady and raise their morale. It was a tactic resorted to only when stakes were high.

When the group were within javelin range, a great cry went up from the legionaries. Tarquinius pointed; they peered to see what the noise was about.

Surena had been generous in letting the mercenaries go, but he was now about to use his greatest weapon against Crassus. A troop of cataphracts had ridden into the centre of the ground between the armies. Their chain mail glinted and flashed in the sunlight: a magnificent sight. But this time they had a different purpose. In the lead, a rider brandished Publius' head on a spear, brutal evidence of what the Romans could expect.

The enemy horsemen rode close enough to let every soldier see exactly whose head had been taken. Another roar of despair rent the air. The Romans had lost not just half their cavalry and two thousand infantry.

Crassus' son had been slain.

Behind the Roman centre, Crassus heard the outcry, but failed to respond. Having watched Publius' cavalry charge being cut to pieces, the general's spirits had plummeted. His son's fate was unknown and there was little chance of any help in deciding the legions' next move. Other than that troublesome Longinus, none of his senior officers seemed to have any idea what to do. Their intimidation had been too thorough. But Crassus was damned if he would listen to a mere legate.

Unsure what to do next, he pushed his horse up to the back ranks, to find out what was going on. Waves of fear rippled through the men at the sight of his black cloak. It was a bad omen to wear this colour at any time, let alone when leading an army into battle.

Ignoring the frightened soldiers, Crassus focused with difficulty on the cataphracts riding past. Publius' blood-soaked features bobbed up and down on the spear.

Crassus froze in shock. Then, overcome by grief, the arrogant general disappeared; a shrunken man sagged over his pommel. Great sobs racked the would-be Alexander.

Making the most of their trophy, the Parthians moved on.

Remembering all the bad omens, legionaries nearby glanced at Crassus nervously. The repeated signs from above had affected even those who weren't superstitious. The storms at sea. The bull's heart. An eagle standard turning to face the rear. Vultures following the column for days. The Nabataeans' treachery. And now Publius was dead.

It was obvious. The gods had damned Crassus' campaign.

The huge army stood motionless, the trumpets silent as Publius' head continued its ghastly journey along the front lines. Then men began to waver and break rank, looking for ways of escape. Positioned to their rear, junior officers armed with long staffs beat them back into position, but could not stem the rising fear. Cold fingers of terror were stealing into exhausted hearts and it was contagious. The soldiers needed immediate leadership, but none was forthcoming.

The murmurs began, spread, rose to panic-stricken shouts.

'The general has lost his mind with grief!'

'Crassus has gone mad!'

'Fall back!'

'Shut your damn mouths!' screamed the centurion near Romulus, wielding his cane viciously. 'The next man to mention retreat will end with my gladius in his belly! Stand fast.'

Cowed by their officers, most of the legionaries fell silent. Discipline was still holding – just.

The troop of cataphracts returned to the Parthian lines. Their quivers refilled, thousands of horse archers immediately began moving towards the Romans. After his master stroke of displaying Publius' head, Surena was now going for the jugular.