But the ships that would carry all these goods away were of more interest to Romulus and Tarquinius. Tied up in their dozens, shallow-draughted fishing boats with small single masts knocked gently against larger merchant vessels with neatly reefed sails. Many of the craft were of unfamiliar shape to Romulus, but the haruspex had mentioned feluccas and native galleys. Here and there he saw sharp-prowed, lateen-rigged ships, their armed, unsavoury-looking crews eyeing each other warily. These were not honest traders. Without a bronze ram or banks of oars, the dhows still reminded him of Roman triremes. Of fighting ships.

It was a group of men from one of these that Tarquinius was studying intently.

But what did it matter anyway? Once more, Romulus’ misery settled over him like a cloak. He briefly considered letting himself fall in, to sink beneath the slick, greasy surface. Then his guilt might end.

‘It is not your fault that he died,’ said the haruspex softly.

The words sprang to Romulus’ lips unbidden. ‘No,’ he spat. ‘It’s yours.’

Tarquinius recoiled as if struck.

‘You knew,’ shouted Romulus, uncaring that men’s heads were turning in their direction. ‘Since that night after Carrhae. Didn’t you?’

‘I-’ the haruspex began, but it did not stop Romulus’ flow of rage. It had been pent up since the battle – since leaving Brennus to face an elephant on his own.

‘We could have gone with Longinus and marched back to the Euphrates.’ Romulus pressed his fists against his head, wishing that were the truth. ‘At least they had a chance of escaping. But you said that we should stay. So we did.’

Tarquinius’ dark eyes grew sad.

‘And then Brennus died, when he did not need to.’ Romulus closed his eyes and his voice tailed away into a whisper. ‘He could have escaped.’

‘And left you?’ Tarquinius’ voice was low but incredulous. ‘Brennus would never have done that.’

There was a long silence, during which the onlookers grew bored and turned away.

Even that was probably part of Tarquinius’ plans, Romulus thought bitterly. Avoiding attention was always a good idea. At that very moment, however, he did not care who saw or heard their conversation.

Several weeks had passed since their journey from the battlefield, yet now, as then, Romulus was consumed by one thing. Had the haruspex known about, or planned, their whole experience since joining Crassus’ army? Had he and Brennus been nothing more than unknowing pawns, acting out an already written script? It was a question that Tarquinius repeatedly refused to answer. Overcome with grief after Brennus’ heroic sacrifice, Romulus had simply gone along with him. Swimming across the Hydaspes was an ordeal in itself, and the passage south that had followed was even more arduous. Without helmets, chain mail or shields, with only their gladii and Tarquinius’ battleaxe for protection, the two weary soldiers had been forced to travel mainly by night. Otherwise their pale skins and inability to speak the local languages would have marked them out as foreigners, easy prey for even the ignorant villagers whose land they passed. Strangers such as they might carry money or riches.

Fortunately, their combined skills had been sufficient to hunt or steal just enough food to live on without often being detected. It was trying to avoid centres of human population that was hardest. The fertile land near the River Indus, which the Hydaspes had joined, was densely inhabited. Most communities were situated close to the river, the main source of water for agriculture and life in general. And the pair had no choice but to follow its course. The grief-stricken Romulus had no idea which way to go, and even Tarquinius knew only to head south. The Periplus, the ancient map given to him by Olenus, had sketchy details for this part of the world. Consequently, they had to creep their way around all the villages in pitch darkness, risking discovery each and every night. More than once, dogs had raised the alarm, forcing them to retreat and wait for another chance, as lurking thieves do.

The process was mentally and physically exhausting for both, and five days later they had made the decision to steal a small boat from a fishing hamlet. It had proved to be the riskiest but most profitable move of the entire journey. None of the sleeping denizens had noticed until it was far too late, and those who did awaken were not foolish enough to pursue the pair along the river in the pitch black. Romulus’ and Tarquinius’ new boat had two crudely made oars, which meant that they could travel whenever they chose. They stayed close to the shore, only risking the strong current mid-river when other vessels were encountered. The ragged nets on board had allowed them to fish daily, providing a simple, if boring diet.

Conversation had been limited after Romulus had accused Tarquinius of failing to prevent Brennus’ death. Taking the haruspex’ refusal to answer as a confession, Romulus had lapsed into a furious silence that was only broken by questions about food or their direction of travel. As a result, their arrival in the exotic metropolis of Barbaricum had been muted, but neither could deny that it was an important milestone. Cities had become an alien place to them.

It was more than a year since they had been paraded through the streets of Seleucia, the capital of Parthia. Margiana, where the Forgotten Legion had served as a border force, held nothing more than a few towns and the tiny settlements along the Indus were scarcely more than hamlets. In contrast, this massive city was protected by strong walls, fortified towers and a large garrison. As in Rome, most inhabitants were poor labourers or shopkeepers, but instead of living in blocks of cramped flats, they dwelled in primitive one-storey mud huts. There was no sign of a sewage system: rubbish and human waste lay everywhere on the muddy streets.

Barbaricum also lacked the proliferation of huge temples that existed in Rome, but it was still an impressive sight. Flashy palaces abounded, the homes of wealthy nobles and merchants. And the enormous covered market near the docks was a sight to behold. The portion near them formed just a tiny fraction of the whole bazaar. Romulus had been awestruck by the variety of goods, living or inanimate, human or animal, on offer there. Yet this was one of India’s main trading centres, a seaport where every kind of merchandise under the sun came to be bought and sold before being transported away to far-off lands. It was living, breathing proof that Rome was only a tiny part of the world.

As if reminding him of that, a line of heavily laden porters emerged from the maze of narrow alleyways that opened on to the harbour. Led by a self-important-looking man in a short, belted robe who was carrying a bamboo cane, they pushed through the clamouring crowds, eventually reaching a large merchantman with two masts which lay alongside the main dock. Following close behind the column was a group of guards armed with spears, swords and clubs. They fanned out protectively as the valuable merchandise was lowered to the ground. There was a brief pause as the merchant conferred with the ship’s captain and then the porters began the laborious task of carrying their loads up the narrow gangplank.

Romulus felt a thrill of excitement. From here, ships sailed westwards once a year, on the monsoon wind, to Egypt. And from there, a man could journey to Rome. All they needed now was to find a captain who would give them passage.

So much had happened to bring him here, thought Romulus. He and Tarquinius had survived the carnage of Carrhae and the epic march east, evaded murderous attacks by other legionaries and escaped annihilation by an Indian king’s army, finally ending up in a place whence returning home was actually possible. It seemed incredible – a virtual miracle, in fact. But the price exacted was heavy: apart from the countless thousands in Crassus’ army and the Forgotten Legion who had died, first Felix and then Brennus had lost their lives. The death of the man who meant more to him than anyone apart from his mother and Fabiola had been a particularly devastating blow. Guilt weighed down on Romulus’ shoulders. Two friends had died to give him this opportunity and there was nothing he could do about it.