Volisios stood beside him. 'You don't need to be afraid of them,' he said with faint contempt. 'Most of them have been whipped so hard all their lives that even if you took their chains away they wouldn't raise a hand against you. You have to do it, you know.'

'What?'

'Treat them harshly. I know what you're thinking, that this is a brutal place. But I have to crush my slaves to get every last drop of blood out of them, because the tax men squeeze me for profits. It's the way things are.'

'But is this the only way?' Thalius murmured, suddenly appalled by Volisios's bloodless rationalising.

Volisios looked at him blankly. 'Of course it's the only way. This is the way things are. This is the way they have always been, and always will be.'

'Must they, overseer?' Thalius, if unworldly, was an imaginative, deep-thinking man, and it had been a day of vivid impressions for him: the hellish conditions of the mine, the miserable condition of his slave cousin, the mighty churning engines in the mine shaft. Now he plucked a speculation out of the air. 'Consider this. Down there you have men digging out ore, and waterwheels pumping out the shafts. What if you installed more waterwheels, and used them to dig out your ore?'

'Impossible,' Volisios said immediately.

'Not to an engineer ingenious enough to make a water-powered organ, surely. What if the mine could mine itself, as an amphitheatre organ plays without human hands? Can't you see it? With such a source of wealth, isn't it possible that the empire could grow rich again, rich and strong-and nobody would have to suffer for it?'

Volisios frowned. 'Are you a fan of gadgets, then, Thalius? I myself have always been drawn more to episteme than to techne-true, deep knowledge rather than to low cunning and trickery.'

Thalius was irritated by this Greek-quoting snobbery. 'Must we be so limited in our thinking? I'm more interested in a single waterwheel than a thousand long-dead Greek philosophers!'

'Well, that's up to you.'

'Yes, but what if-?'

'Besides, what would we do with all the slaves? Free them? They would butcher us in a heartbeat.' And, laughing, Volisios turned away.

Thalius peered out of the window, listening to the grinding noise of the giant machines deep underground and the groans of human misery, and his rudimentary vision of a technological future evaporated.

At last Tarcho brought in the boy.

Audax had been washed, that pale hair cut and brushed, and he was dressed in a fresh tunic. He was probably as clean and presentable as he had ever been in his life, Thalius reflected. But he was nothing but skin and bones, and there were marks, like the bruising around his mouth, that no amount of water would wash away. But Audax clung to Tarcho's hand, and Thalius saw that Tarcho was finding a way to win his trust.

It struck Thalius that he had not yet heard the boy speak, not one word.

'Apart from that scarring on his back his health is reasonable,' Tarcho said now. 'Nothing a bit of sunshine and some decent food wouldn't cure.' He said more cautiously, 'He has some bruising around the thighs, however. His mouth and throat are damaged, and-'

'Enough,' Thalius snapped.

Tarcho said to the overseer, 'I know what goes on in these places. A pretty boy like this will be traded for a morsel of food.'

Volisios said, 'What did you expect? But things are more complicated than you probably understand, soldier. The men, trapped in the dark and the damp, turn to each other for comfort, for there is nothing else. Why, some of our longer-lasting workers have "marriages" that have fared better than my own! This boy may have been hurt, but he's just as likely to have been treated with kindness.' But he didn't look at the boy as he said this, or ask him to confirm or deny it.

Thalius asked carefully, 'And the marks on his back?'

Tarcho nodded to the boy. Audax turned around and lifted up his tunic, exposing skinny legs, flat buttocks, and a back covered with livid scars. But now the dirt was off Thalius could clearly see the shapes of the letters, sixteen of them, in their square grid:

Tarcho scratched his head. 'And is this what you came looking for?'

'It must be.'

'The boy has no memory of having received this tattoo.'

'I'm not surprised,' Thalius said. 'See how the letters are stretched, distorted? He must have received these markings when he was very small, an infant perhaps. As he has grown the marks have grown with him. Perhaps the marks were copied from his own father at his birth, and his father before him…' Thalius imagined it: a slave painfully pricking out letters into the raw skin of his child, perhaps with a bit of quartz from the gold seams, and rubbing in dirt or vegetable dye.

It had been the curse of Severa's sentence to slavery that her grandchildren would not even be literate. So with the Prophecy burned, its words would be lost after a generation, two, three. But evidently, Thalius thought, excited, somebody had come up with a way of preserving at least some of the text, inscribed into the very bodies of children. Thalius had read something of Severa, his remote grandmother of so many generations ago; perhaps it was that hard woman herself who had come up with this way of saving the Prophecy in blood and pain.

Volisios had become a lot less respectful since Thalius had admitted he was no government inspector. 'So you have what you wanted. What will you do with the boy? Throw him back down into the pit? Or would you like him to warm your own bed first?'

'You disgust me,' Thalius snapped.

But Tarcho said, 'Actually he has a point, Thalius. Slaves are expensive, you know.'

'He is blood,' Thalius said. 'Distant blood, but blood. I won't leave him here to be raped to death. Name your price, overseer.'

Volisios nodded and, business-like, reached for a wooden note block and a pen.

The boy watched all this, wide-eyed; surely he hadn't understood a word.

Tarcho studied the tattoo again. 'But what does it mean?'

'I don't know. Not yet. It's clearly some kind of acrostic.'

'A what? Never mind. And where will this quest of yours lead us next?'

'To Rutupiae.'

'The east coast? What for? Who will be there?'

Thalius said simply, 'Constantine.'

V

It would take many days for Thalius, Tarcho and Audax to travel from Dolaucothi in the west of Britain all the way to Rutupiae in the extreme east, where Thalius intended to gain an audience with the Emperor. With the boy in Tarcho's care they set off, the three of them in Thalius's cart.

Once they had crossed the Sabrina river they passed out of what Tarcho called 'soldier country', where wild men of the hills chased flocks of ragged sheep between the walls of Roman forts, to the more settled lands of the south and east. The cart rolled along busy, well-maintained roads through farmland-rather a lot of it abandoned.

On the way to Durovernum Cantiacorum and Rutupiae they stopped in towns, including a night in Londinium. All the towns looked the same, with their basilicas and their forums, their baths and their townhouses: all miniature models of faraway Rome itself. But many of the public buildings had seen better days. Shabby old basilicas had been turned into granaries or stock sheds or arms dumps, and sometimes you could see fire damage nobody had bothered to fix. Even in Londinium there was a monumental basilica only half finished and apparently abandoned; entwined by vines and carpeted by grass and weeds it seemed to be turning into a ruin before it had even been completed. And a new wall ran along the north side of the river, cutting through the wharves and dock facilities that had once served the grand cross-provincial trade routes. People, over-taxed, just didn't put their money into civic developments the way they once had. Most wouldn't even pay to keep the public sewers working, or to clear away rubbish. As a result, the towns stank.