I addressed her. ‘I am writing my final report. I shall write it now, this afternoon; then I shall leave here and play no further part. It is your choice. If you tell me the rest of the story, I promise I will recommend to Manlius Faustus that the two of you have immunity from prosecution, your freedom, and such other rewards as he and the Temple of Ceres see fit.’

I meant it. Faustus had given me authority to offer as much.

‘Three of us,’ begged Daphnus.

‘Three?’

‘My brother, Melander.’

I said it was good to see family loyalty. Far be it from me to separate twins in the city of Remus and Romulus; Faustus would make it a triple amnesty.

Yes, I know about Remus being murdered by his twin out of jealousy.

So they settled down to confess to me. Daphnus started the story, under Amaranta’s watchful eye. I knew the beginning, from Cosmus invading the bedroom and exploding, through the other slaves discovering what he had done – ‘Too late to stop him, which we would have tried –’ then their deciding with Polycarpus that the murders of Aviola and Mucia put them all at risk.

‘Did none of you ever think of handing Cosmus over?’

‘Nobody blamed Myla nor Cosmus,’ said Amaranta. ‘None of us cared for either of them much, but we could see that Myla had been treated badly. She didn’t have enough imagination to see she was in a good home and things could have been far worse. Cosmus neither. He was really lucky Polycarpus took him. Cosmus never saw it that way. He just grew up hating the fact that his father, the master, never wanted anything to do with him. He was always obsessed by that.’

‘He had reached the age when he brooded,’ Daphnus put in. He was young enough to remember his own puberty vividly.

‘Myla was used, for years,’ Amaranta said. ‘Of course she was supposed to endure that sort of thing, but it doesn’t mean she felt nothing. Whenever she was angry about it, she would pour out her heart to Cosmus, making him even more resentful.’

‘They were very close?’ I asked, thinking how Myla had tried to take the blame for Cosmus’ acts, just before she committed suicide.

Amaranta nodded. ‘He convinced himself he killed Aviola and Mucia in defence of his mother, to stop her being sold.’

‘Right. Tell me about the robbers, please.’

Daphnus took up the tale. The fleeting visit by Roscius and his men had given Amaranta the idea to fake a robbery. Some of what the neighbour Fauna had seen from above – people running about with lamps and whispering urgently – happened when the slaves packed up the wine set; they hid it in the chair seat, then hurried the chair out to the unused lock-up. They had to act fast, because they knew they must soon involve the vigiles.