'Because I had seen Dionysius following Olympias, and I had seen Olympias bringing an empty basket up from the sea cave. It occurred to me then that Alexandros was hidden here in Cumae. But tell me, Iaia, did you lead me to Zeno's body to throw me off the scent?'

Iaia spread her hands. 'One cannot always discern the Sibyl's methods; even when the god grants a supplicant's desires, he doesn't always use the means expected to accomplish his end. You might have assumed Alexandros was dead and proceeded from that assumption. Instead, here you sit, in the same house with Alexandros. Who can say this is not what the Sibyl intended, even if it is not what I expected?'

I nodded. 'You knew, then, of Zeno's fate, and where he could be found. Did Olympias know?'

'Yes.'

'And yet Olympias seemed genuinely shocked when we discovered Zeno's remains.'

'Olympias knew of Zeno's fate, but she had not seen his body, as I had. I never intended for her to see it; I intended for you to visit Lake Avernus without her. Instead she went with you, and in horror she cast his remains into the pit. I have no doubt that this, too, was the will of the god.'

'And I suppose it was the will of the god that brought Alexandros to your door in the first place, on the night of the murder?'

'Perhaps we should let Alexandros speak for himself,' said Iaia, who cast a sidelong look at the young Thracian. 'Tell Gordianus what transpired on the night of your master's murder.'

Alexandros reddened, either because he was unused to speaking to strangers or because of the memory of that night. Olympias drew closer to him and laid her hand on his forearm. I wondered at the casual way she displayed her intimacy with a slave in the presence of a Roman citizen. In the sea cave I had caught them unaware in the middle of coitus, and she had been unembarrassed, but fear and surprise had ruled her then and might have overridden her normal judgment. I was more impressed by the public affection and tenderness she willingly gave Alexandros before Iaia and myself. I marvelled at her devotion, and at the same time despaired for her; how could such an ill-begotten love end in anything but misery?

"That night,' Alexandros began, his harsh Thracian accent overshadowed by the intensity with which he spoke, 'we knew that Crassus was on his way. I had never seen him, I was new in the household, but I had heard much of him, of course. Old Zeno told me that the visit was unexpected and had come about on very short notice, and that the master was unprepared, very nervous and very unhappy.'

'Did you know why Lucius was unhappy?'

'Some irregularity in the accounts. I didn't really understand.'

'Even though you helped Zeno sometimes with the ledgers?'

He shrugged. 'I can add figures and make the proper marks, but I seldom knew what it was that I was adding. But Zeno knew, or thought he did. He said that the master had been busy with some very secret business, something very bad. Zeno said the master had done things behind Crassus's back and that Crassus would be angry. That afternoon we were all three busy in the library, going through the accounts. At last the master sent me from the room; I could tell he wanted to say things to Zeno that I shouldn't overhear. Later he sent Zeno away as well. In the stables I asked Zeno what was happening, but he only brooded and wouldn't talk. It began to grow dark. I ate and helped the other stablemen to look after the horses. Finally I went to sleep.'

'In the stables?'

'Yes.'

'Was that where you normally slept?'

Olympias cleared her throat. 'Alexandros usually slept in my room,' she said, 'next to Iaia's, in the house. But that night Iaia and I were here in Cumae.'

'I see. Go on, Alexandros; you were sleeping in the stables.'

'Yes, and then Zeno came to wake me. He carried a lamp and poked at my nose. I told him it couldn't be morning yet; he said it was the middle of the night. I asked him what he wanted. He said that a man had ridden up from nowhere and tethered his horse by the front door, then had gone in to see the master. He said they were both in the library, talking in low voices with the door shut.'

'Yes? And who was this visitor?'

Alexandros hesitated. 'I never saw him myself, not really. You see, that's the strange part. But Zeno said… poor Zeno…' He furrowed his thick eyebrows and stared intently into space, caught up in the remembrance.

'Yes,' I said, 'go on. What did Zeno tell you? Why did you flee the house?'

'Zeno said he had gone into the library. He had rapped gently on the door and thought he heard his name spoken, so he stepped inside. Maybe he didn't hear his name at all, or maybe the master was telling him to go away; Zeno was like that, he had a habit of stepping in when he wasn't wanted, just to have a sniff at what was happening. He said the master spun around in his chair and told him to get out – yelled at first, then lowered his voice very quickly and cursed him in a whisper.'

'And the visitor?'

'He was standing by the shelves, looking through some scrolls with his back to the door. Zeno didn't really see him, but he saw that he was dressed in military garb, and he saw the man's cloak thrown over one of the chairs.'

'The cloak,' I said.

'Yes, just a simple dark cloak – but one corner had an emblem on it, a seal pinned to the cloth like a brooch. Zeno had seen it plenty of times before; he said he'd know it anywhere.'

'Yes?'

'It was the seal of Crassus.'

'No,' I said, shaking my head. A throb of pain passed through my skull with such power that I finally reached for the cup of willow bark and nepenthes and drank it down.

'No. That makes no sense at all.'

'Even so,' Alexandros insisted, 'Zeno said it was Crassus in the library with the master, and the master's face was as white as a senator's toga. Zeno began to pace up and down in the stables, shaking his head with worry. I told him there was nothing we could do; if the master had got himself into trouble, that was his problem. But Zeno said we should go and stand outside the library door and listen. I told him he was mad and rolled over to go back to sleep. But he wouldn't leave me alone until I got up from the straw and put on my cloak and stepped into the courtyard with him.

'It was a clear night, but very windy. The trees thrashed overhead, like spirits shaking their heads, whispering no, no. I should have known then that something terrible was afoot. Zeno ran ahead to the door and opened it. I followed him.' Alexandros wrinkled his brow. 'I have a hard time remembering all that happened next, it happened so fast. We were in the little hallway that leads to the atrium. Suddenly Zeno backed against me, so hard he almost knocked me down. He sucked in a breath and started blubbering. Over his shoulder I saw a man dressed like a soldier down on his knees, holding a lamp, and beside him was the body of the master, his head all crushed and bloody.'

'And this man was Crassus?' I said, disbelieving.

He shrugged. 'I only glimpsed his face for an instant. Or perhaps I didn't see his face at all; the lamp cast strange shadows and he was mostly in darkness, I think. Even if I had seen him clearly, I wouldn't have recognized him. I told you, I had never seen Crassus. What I remember looking at was the master – his lifeless body; his broken, bleeding face. Then the man put down his lamp and sprang to his feet, and I saw his sword, leaping like a flame in the lamplight. He spoke in a low voice, not frightened, not angry, but cold, very cold. He accused us of killing the master! 'You'll pay for this!' he was saying. 'I shall see both of you nailed to a tree!'

'Zeno grabbed me and pulled me out the door, across the courtyard, into the stable. 'Horses!' he was saying. 'Flee! Flee!' I did what he said. We mounted and were out the door of the stables before the man could follow. Even so, Zeno rode like a madman. 'Where can we go?' he kept saying, shaking his head and weeping like a slave about to be whipped. 'Where can we go? The poor master is dead and we shall be blamed!' I thought about Olympias, and remembered Iaia's house in Cumae. I'd been here a few times before, carrying supplies back and forth.