The complex was far more than a library or a storage place for scrolls. It was a combination of school, shrine and museum, also containing immaculate gardens, a richly stocked zoo and an observatory. Naturally, the temple was dedicated to the Muses, and was overseen by a priest of high rank. For generations, Greek scholars from all over the Mediterranean had come to the library as paid tutors, working together and sharing their knowledge with those who came to learn. Men who knew far more than Tarquinius did had spent years here: Archimedes, studying the rise and fall of the River Nile and inventing the screw which could lift water up great heights; Eratosthenes of Cyrene, who lectured on the route to India by sailing west from Hispania, who posited that the world was round and who had calculated its circumference and diameter. Others had propounded theories about the sun's effect on the planets and stars, or had advanced medical science by their study of human anatomy.

Humility became a new emotion for Tarquinius as he paced the covered walkways of the library's various wings, discovering the existence of more information than he could absorb in a lifetime of study. To him, the shelves filled with linen- and leather-covered scrolls and parchments were like all the gold and jewels in the world. Even though the majority of the information had been catalogued, he found scant word of the Etruscans. A few fragments of crumbling papyrus referred to a people who had journeyed from the lands beyond Asia Minor. There was mention of a city called Resen on the River Tigris, and little else. Nothing to fill in around these skeletal details, which Tarquinius already knew from Olenus. In turn this made him wish that he'd had an opportunity to do some investigation after Carrhae. It was a futile thought, for he, like all the other Roman captives, had been kept under lock and key day and night when in Seleucia. Soon Tarquinius began dreaming about a return trip to Parthia.

Perhaps that was where his future lay? While part of Tarquinius' heart rejoiced at this thought, much of it ached at its utter finality. Would he ever see Romulus again? Although there was no guarantee of a reunion by remaining in Alexandria, the haruspex was reluctant to leave until he unearthed, or was given, some kind of meaningful sign of his purpose.

For weeks, Tarquinius concentrated his search in the library section which contained material on astronomy and history. It was no good. He found nothing. Keen to keep a low profile, he did not ask too much of the librarians, translators and scribes, who tolerated his presence with reluctance. It was Tarquinius' fluent Greek and medical knowledge which had allowed him entry in the first place, but that did not mean that they liked the silent, scarred stranger wandering up and down the covered walkways, or sitting alone, watching the debates between the resident scholars. He did not fit in.

There was, however, one scribbler, as the translators were known, who enjoyed Tarquinius' company. Aristophanes was a stout, balding Greek in late middle age, whose main interest was in astronomy. Like his colleagues, he wore a nondescript off-white short-sleeved tunic. Stooped from a lifetime of leaning over documents, his fingers had been stained black from the ink in his reed stylus. Aristophanes' work area was one of the small courtyards which bordered the book-lined corridors. Perched on a mat surrounded by scrolls and parchments, he deftly copied ancient tracts on to clean pieces of papyrus each day. This part of the library was also where the haruspex spent a lot of time. Inevitably they had spoken; Tarquinius wanted to read a particular text about Nineveh, but could not locate it and had asked the Greek for help. As they searched, a prolonged debate about the merits of papyrus versus those of calf-skin parchment developed. Although they never found the relevant scroll, a friendship developed, one based on scholarly topics, and which avoided personal matters. Other than the fact that he was Etruscan, Tarquinius mentioned little about his past, and Aristophanes was content not to ask.

That morning was no different, and the two men resumed their discussion of the previous day, about whether it was possible to accurately measure the movement of the stars.

'They say that there's a box-like device on Rhodes which shows how the sun, moon and planets travel through the sky,' the scribbler confided. 'Made of metal, with dozens of little hidden wheels and cogs which move in unison. Apparently it can even predict lunar and solar eclipses. Not sure I believe it myself.'

Tarquinius laughed. He'd heard rumours of such a thing when visiting Rhodes himself.

Aristophanes frowned. 'What?'

'Look around you. Think of the wealth of knowledge which has been gathered here,' he replied. 'Why wouldn't that appliance exist?'

'Of course, you're right.' Aristophanes smiled ruefully. 'I've spent too long here. Can't see what's in front of me any more.'

Tarquinius thought for a moment. While the data he studied in the library was fascinating, all too often it felt sterile, even dead. 'Rhodes, you say?' he asked.

Aristophanes nodded. 'In the Greek school there. One day I'll visit it,' he said wistfully.

Perhaps I should also go, reflected Tarquinius. He'd stolen enough for the passage. Suddenly, the library's tranquillity was broken from outside by the distinctive tramp of men marching in unison. The noise came to a halt by the main gate, and was followed by the hammering of a weapon butt on the timbers. Shouted commands rang out, demanding entry.

Aristophanes looked perturbed. Even the recent fighting had not affected the library's status as an island of calm in the city. 'What in the name of Zeus do they want?'

Tarquinius was on his feet before he knew it, clutching for a sword that wasn't there. The orders had been given in Latin, not Greek or Egyptian. That indicated Roman soldiers were present, which meant trouble. Legionaries might ask awkward questions. He felt the air about him move. Danger, the haruspex thought. Was it to him, though, or to someone else?

'What's wrong?' Aristophanes had seen his response. 'Are they after you?'

Calm down, thought Tarquinius. Few, if any, Romans in the city would recognise me. He took a deep breath. 'Not exactly,' he said slowly, knowing that the only exits apart from the main entrance were locked. He'd tried them already, seeking an escape route in advance – in case it should ever be needed. 'I don't like them, that's all.'

The Greek gave him a sceptical look. He knew that Tarquinius was from Italy, and had gleaned that he'd served in the army. There was more occurring here than his friend was letting on. Yet, like most residents of the city, whether Egyptian or Greek, Aristophanes had little love for the new effective rulers with their arrogance, crude manners and martial tendencies. 'Go back under the portico,' he advised quietly. 'Even if they come in here, the sunlight is so bright that they'll only see a shadow. Just another scholar studying some old tome.'

Grateful, Tarquinius rolled up the tract on Assyria which he'd been perusing and did as Aristophanes said. Facing the rows of shelves, he could peer over his shoulder at anyone who came into this wing. What then, though? There was still no way out. With his heart thudding in his chest, he looked up at the patch of sky that was visible overhead. The air was calm, and the clouds made no sense. Tarquinius cursed under his breath.

To his surprise, the soldiers who clattered into the courtyard a few moments later were a mixture of Romans and Egyptians. First came two squads of ten well-presented legionaries, then the same number of royal guards, resplendent in green tunics, Greek helmets and bronze breastplates. Taking half of the area each, the two groups spread out in a protective screen, their spears and swords ready. Aristophanes and his accoutrements were simply stepped over and ignored. An officer whistled the all-clear and in walked a striking young woman; she was accompanied by several fawning courtiers and senior librarians. Tarquinius' mouth opened. Knocking his pots of ink flying, Aristophanes jerked up and prostrated himself face first upon his reed mat. He had no time to warn Tarquinius, but there was no need.