Titianus had to treat them politely, especially with me watching. They equally politely told him what little they knew. They had seen Polycarpus go into the empty premises. They exchanged greetings while he was opening up the shutter, but he was still in there on his own when the two North Africans left. He had pulled the shutter closed after him, except for a space of about a foot – which I thought was odd, because whatever he wanted to do there, the place would surely have been too dark.

‘Graecina, did you know why your husband came down here?’

Something about the carrying chair, but Graecina did not know what. I went and had a look at it. The soiled seat, a padded drop-in rectangle on a wooden frame, had been lifted out. If there had been a bucket of water and a sponge, that would have answered the question for certain, but there were no cleaning materials.

Apart from being bloodstained, I could see nothing odd about the cushion. I swung open the chair’s half door and inspected inside. There was a compartment underneath the seat. It was empty.

As I emerged, Titianus spotted Cosmus loitering and remembered him from the Aviola incident. Apparently it was Cosmus Polycarpus sent that night to the station house.

‘Come here, you!’

Cosmus looked around as if he thought Titianus meant someone else, then loped across. He was a sturdy lad, just growing his first moustache. The vigilis muttered under his breath to me, which at least meant I was now a colleague he could grumble with.

Titianus questioned the slave with the air of a man who had wasted effort on the hopeless many times. He had an impatient, bullying approach which only drew out answers he clearly expected. Cosmus was the kind of slave who drifted about the neighbourhood, yet never heard or saw anything.

Cosmus said he had been sent downstairs by Polycarpus that morning to carry water to the apartment, so he was either away at the fountain (out of sight further down the street) or indoors out of earshot at the time when someone must have visited Polycarpus in the lock-up. Just before I arrived and saw him by the leather shop, Cosmus had been inside the house talking to Myla.

He was useless as a witness. Titianus could only roll his eyes and let Cosmus go.

I told him, ‘See if Graecina wants you to do anything. Then stay with her. She needs support.’

To make sure, I myself led him over to Graecina who was talking to the undertaker. She confirmed the story about Polycarpus sending Cosmus to fetch water, as he did every day.

Titianus and I went indoors to question Myla. She was in the kitchen nursing her baby. She made sure Titianus had an eyeful. He was more tolerant with her than I would have been, perhaps because he was riveted by the breast-feeding. Typical.