Suddenly Fabiola felt worried. What if Romulus appeared in the arena? Jupiter, Greatest and Best. Keep my brother safe from harm. The prayer had become a personal mantra over the last three years. She breathed deeply, forcing herself to be calm. If Jupiter was merciful, Romulus would not be one of today's fighters.

The appeal was answered. None of the armoured men who maimed and killed each other in the hour that followed looked remotely like Romulus, but the bloody spectacle was still distressing. Although she fantasised about revenge on Gemellus and the man who had raped her mother, Fabiola did not like violence. The crowd's roars of approval at more brutal moments were sickening. Images of Romulus bleeding on the sand came frequently to mind, images that she had managed to keep from her mind till now. But for all she knew, her twin brother might already be dead. When the display came to an end, Fabiola felt a real sense of relief. There would be a break before two of the most popular gladiators in the city took each other on.

Brutus was chattering on about technique and the skills of various types of fighters.

Fabiola listened vaguely, nodding at regular intervals as if interested. She was having trouble controlling the grief bubbling inside her.

'Course there hasn't been a decent champion since that Gaul disappeared.'

She pricked her ears. 'Who?'

'Brennus, his name was. Size of two men, but skilful with it.' Brutus' face lit up. 'With a legion of soldiers like that Gaul, Caesar could conquer the world.'

'What happened to him?'

'Got ideas above his station. He and another gladiator killed a noble outside the Lupanar about a year ago,' said Brutus.

Fabiola's stomach clenched. Romulus! He might still be alive.

'Remember that? Stocky redhead called Caelius, I think.'

'Oh yes,' she said, feigning surprise. 'Broke the doorman's nose too.'

'Complete waste,' sighed Brutus. 'If either shows his face in Rome again, he'll be crucified.'

Fabiola was about to ask more, but a loud fanfare interrupted.

Pompey had arrived.

Chapter XX: Invasion

The Euphrates, Mesopotamia, summer 53 BC

Like all Roman leaders, Crassus consulted soothsayers before momentous occasions and the invasion had begun with sacrifices to the gods. A good omen for crossing the river was crucial.

Just before dawn, an old priest had led a large bull into the open space before Crassus' command tent. Dressed in a plain white robe and surrounded by acolytes, he had watched the unconcerned beast chew some hay. Hundreds of soldiers gradually assembled, picked from every cohort in the army to witness that the campaign had been sanctioned by the gods. Having persuaded Bassius to let them attend, Tarquinius and Romulus stood in their midst.

There was a sigh of expectation when Crassus appeared at the doorway of his tent. The guards snapped to attention, their weapons and armour polished even brighter than usual. The general was a short, grey-haired man in his early sixties with a beaked nose and piercing gaze, clad in a gilded breastplate, red cloak and horsehair-crested helmet. Studded leather straps protected Crassus' groin and upper legs and an ornate sword hung from his belt.

Unlike Pompey and Caesar, his two partners in the triumvirate, Crassus did not have vast military experience. But he was the man who had defeated Spartacus. The unprecedented slave rebellion a generation before had almost brought the Republic to its knees. Only Crassus – and to a lesser extent Pompey – had saved it from ruin.

The general was flanked by Publius and the legates commanding each of the army's seven legions, the officers dressed similarly to their leader.

Remembering Julia's scar, Romulus angrily nudged the Etruscan when he saw Publius.

Concentrating hard, Tarquinius frowned. 'Be quiet and watch.'

The priest looked at Crassus, who nodded once.

Muttering incantations, he approached the bull, which was still chewing contentedly. Two acolytes grabbed the rope around its head, while others pressed in close, preventing escape. Realising far too late that something was wrong, it bellowed angrily. Despite its huge strength, the men extended the bull's head forward, exposing the neck.

From inside his robe, the priest produced a wicked-looking blade. With a quick slash, he cut the throat, releasing a fountain of blood on to the sand. A silver bowl was swiftly placed under the stream, which filled it to the brim. The helpers let go and the bull collapsed, kicking spasmodically. Standing back, the old man peered into the red liquid.

Everyone present held their breath as the contents were studied. Even Crassus remained quiet. The Etruscan stood motionless, his lips moving faintly and Romulus felt a shiver of unease.

The soothsayer stood for a long time, muttering to himself and swirling the blood. Finally he scanned the sky.

'I call on Jupiter, Optimus Maximus! I call on Mars Ultor, bringer of war!' The priest paused. 'To witness the omens from this sacred beast.' Again he waited, gazing intently.

Crassus anxiously watched his men. It was vital that they thought the campaign would be successful. A slight soldier with blond hair and single gold earring caught his attention. Carrying a large battleaxe, he was dressed like an irregular. The man stared back without fear or deference, apparently ignoring the ceremony.

Crassus felt goose bumps rising on both arms and suddenly remembered the Etruscan bronze liver he had tried to buy many years previously. The soldiers he had sent on that mission had all died shortly afterwards. Terror constricted his throat and he turned away. The mercenary was regarding him as he imagined the ferryman might.

No one else had noticed.

'The omens are good!'

A great sigh of relief swept through the gathering.

'I see a mighty victory for Rome! Parthia will be crushed!'

Wild cheering broke out.

Crassus turned to his legates with a smile.

'Liar,' hissed Tarquinius. 'The blood showed something else altogether.'

Romulus' face fell.

'I'll tell you later. The ceremony's not over yet.'

They watched as the priest cut open the animal's belly with a sharp knife. More favourable predictions followed as shiny loops of gut came spilling on to the sand, followed by the liver. The climax came once the diaphragm had been cut, allowing access to the chest cavity. Reaching deep into the steaming carcass with his blade, the soothsayer cut and pulled for a few moments. At last he stood and faced the officers, robes saturated with blood, his arms red to the shoulder. In both hands sat the bull's heart, glistening in the rays of the rising sun.

'It beats still! A sign of the power of Crassus' legions!' he yelled.

All the legionaries roared approval.

All except Tarquinius and Romulus.

Arms outstretched, the old man approached Crassus, who waited with an expectant smile. The omens had been good. Soldiers would hear the news from those watching, spreading it through the entire army faster than he ever could.

'Great Crassus, receive the heart. A symbol of your bravery. A sign of victory!' the priest shouted.

Reaching out eagerly, Crassus stepped forwards. This was his moment. But as he took the bloody organ, it slipped from his grasp, landed on the ground and rolled away from him.

There was a sharp intake of breath from Tarquinius. 'Nobody can deny what that means.'

Crassus moaned. The heart was no longer red. Thousands of grains of sand now coated its surface, turning it yellow.

The colour of the desert.

He stared at the priest, whose features were ashen. Everyone watching had gone rigid with shock.

'Say something!'