'Put the weapon away,' I said wearily. 'I haven't come to hurt you.'

They stared at me, wide-eyed and dubious. There was a softening in Olympias's eyes; only in that instant did she finally recognize me. What must I have looked like, rising up from the spuming tunnel wrapped in tendrils of seaweed, with blood trickling down my face? Alexandros stared at me as if I were a sea monster, and perhaps he thought I was.

'Wait,' Olympias whispered. She laid her hand on Alexandros's arm. 'I know him.'

'Yes? Who is he?' He spoke with a heavy Thracian accent, and there was a wild, desperate note in his voice that caused me to slide my hand nearer to where my own dagger was sheathed beneath my tunic.

'The Finder,' she said. 'From Rome – the man I told you about.'

'Then he's found me at last.' He pulled his arm free. The long blade sliced through a pale shaft of sunlight and glimmered like quicksilver. He drew back against the cave wall and stared at me like a trapped animal.

'Is that what's happened, Gordianus?' Olympias looked at me suspiciously. 'You've come to take him to Crassus?'

'Put the knife away,' I whispered. I began to shiver uncontrollably. I clenched my teeth to stop them from chattering. 'Can you make a fire? I suddenly feel very cold, and a little faint.'

Olympias studied me for a moment, then made up her mind. She reached for a woollen gown and pulled it over her head, then stepped towards me and reached for the hem of my tunic. 'Out of this, first, or else you'll die from the cold more surely than you will from a dagger. No fire, I'm afraid – we can't have anyone seeing the smoke – but we can wrap you in something warm. Alexandros, you're shivering as well! Put that knife away and cover yourself.'

The cave, when I had first glimpsed it, had seemed enormous, stretching away like the Sibyl's cave into unknown space. It was not as large as that, but it did rise to a considerable height and was cut into the stone at an angle that slanted sharply away from the sea, so that the floor was stepped in a number of rocky terraces. Stowed here and there in small nooks were Alexandros's comforts – dirty coverlets, bits of food, utensils, jugs of fresh water, and a plump wineskin. Olympias took me to one of the higher terraces and wrapped me in a wool blanket. When my shivering subsided she offered me some crusts of bread and cheese, and even a few delicacies that I recognized from the funeral banquet; she must have pilfered them from the table and brought them as a treat for Alexandros. I protested that I wasn't hungry, but once I began I could hardly stop eating.

Soon I felt better, though bolts of pain still shot through my head when I moved it too sharply. 'How soon will the opening of the cave be passable? Without serious risk of drowning, I mean?'

Alexandros glanced at the mouth of the cave, where already the foaming tide seemed to have ebbed. 'Not long now. There won't be clear beach beneath the opening for another few hours, but already you could make your way into the water and up to the path without danger.'

'Good. Whatever else happens, I must be there, at the arena. No matter how terrible. And I must find Eco.'

'The boy?' said Olympias. Apparently she had never cared enough to catch his name.

'Yes, the boy. My son. The one who casts such longing looks in your direction, Olympias.'

Alexandros wrinkled his brow disapprovingly. 'The mute boy,' Olympias explained to him. 'I told you about him, remember? But, Gordianus, what do you mean when you say you must find him? Where is he?'

'Last night, when we set out for Cumae, we followed the route we took with you. We were attacked, on the precipice that overlooks Lake Avernus.'

'By lemures?' whispered Alexandros.

'No, by something worse: living men. Two, I think, but I can't be certain. In the confusion Eco disappeared. Afterwards I went searching for him, but my head…'

I touched the tender spot and winced. The bleeding had stopped. Olympias studied the wound. 'Iaia will know what to do for this,' she said. 'But what about Eco?'

'Lost. I never found him, and then I lost consciousness. When I awoke I came here. If he's gone back to Gelina's villa, he may end up at the funeral games by himself. He's seen gladiators fight to the death before, but the massacre – whatever else happens, I must get back before it starts. I don't want Eco to see it alone. The old slaves, and Apollonius… and little Meto…'

'What are you talking about?' Alexandros looked at me, puzzled. 'Olympias, what does he mean by a massacre?'

She bit her lip and looked at me ruefully.

'You haven't told him?' I said.

Olympias gritted her teeth. Alexandros was alarmed. 'What do you mean by a massacre? What are you saying about Meto?'

'Doomed,' I answered. 'All of them, doomed to die. Every slave from the fields and the stables and the kitchens will be publicly slain to satisfy the good people of the Cup. Politics, Alexandros. Don't ask me to explain Roman politics to a Thracian slave, just take my word for it. For the crime of the true killer, whom he cannot find, Crassus intends to have every slave in the household put to death. Even Meto.' Today?'

'After the gladiator contests. Crassus's men have erected a wooden arena in the flatlands by Lake Lucrinus. It should be quite an event, the kind of thing people will talk about from here to Rome for a long time to come, even after Crassus defeats Spartacus and finally gets himself elected consul – and after that, who knows? Perhaps he'll manage to make himself dictator, like his mentor Sulla, and people will still talk about the day he put the slaves of Baiae in their place.'

Alexandros leaned back, aghast. 'Olympias, you never told me.'

'What would have been the point? You would only have fretted and brooded-'

'And perhaps he would have made some grand gesture by returning to Baiae to face Crassus's judgment himself?' I suggested. 'Is that why you didn't tell him, Olympias? Instead you let him think that he merely had to stay in hiding long enough for Crassus to leave, and then he might escape, and you never whispered a word about all the slaves fated to die in his place.'

'Not in his place, but alongside him!' said Olympias angrily. 'Do you think it makes any difference to Crassus whether he finds Alexandros or not? He wants to put the slaves to death – you said so yourself, just now, for politics, to put on a show. Better for Crassus if he never finds Alexandros – that way he can keep scaring people with stories of the murdering Thracian monster who ran off to join Spartacus.'

'What you say may be true now, Olympias, but was it so at the beginning, when Alexandros first fled to Iaia's house? What if you had turned him over to Crassus then? Would Crassus ever have concocted his scheme to avenge Lucius Licinius in such a terrible way? Do you feel no guilt for what you've done, hiding your lover and letting all the other slaves be slain? The old men and women, the children-'

'But Alexandros is innocent! He never murdered anyone!'

'So you say; so he tells you, perhaps. But how do you know, Olympias? What do you know?'

She drew back and sucked in a breath. The lovers exchanged an odd glance. 'You know as well as I that it makes no difference whether Alexandros is innocent or not,' she said. 'Guilty or innocent, Crassus will crucify him if he's caught.'

'Not if I could prove him innocent. If I could discover who did kill Lucius Licinius, if I could prove it-'

'Then – most especially then – would Crassus be certain to put Alexandros to death. And you as well.'

I shook my head and grimaced at the flash of pain across my forehead. 'You talk in riddles, like the Sibyl.'

Olympias looked at the mouth of the cave, where flashes of light were reflected from the churning water beyond. 'The tide has ebbed enough,' she said. 'It's time for us all to go up to the house to see Iaia.'