His name was Pylaemenes. The house steward told me. To my surprise the slaves here seemed indifferent to the man; I had reckoned they would be hostile to an influential outsider – especially one of distinctly foreign appearance whose robe hem needed tacking up but who was probably paid zillions.

'We are used to all sorts,' shrugged the steward, as he took me to find the slave who discovered the body.

This was a distraught waif of about fifteen, now trembling in the corner of his cubicle, hugging his knees. When I entered the bleak compartment, a typical slave cell which he shared with another, he showed me the whites of his eyes like an unbroken colt. The steward picked up a thin blanket and draped it over him, but it would clearly slide off again.

As a witness the lad was useless. He would not speak. It looked as if he did not eat. If nothing was done soon, he was a lost soul.

What could anyone expect? The steward had told me about him. He had been a cheery, useful teenager who then found himself alone in a room with a headless corpse. Born and bred a house slave in a home of refulgent luxury, where the owners were obviously civilised people and he was probably never chastised by more than wounding sarcasm, this was his first meeting with crude death by violence. Pools of still-warm, spreading blood, in one of which he had accidentally stepped, had horrified him out of his wits.

He was the flute boy. His double flute sat on a ledge in his cell. He had gone to entertain Gratianus Scaeva with music while the young master was reading. I guessed he would never play again. 'Does Quadrumatus Labeo have a personal doctor? Someone should take a look at this lad.' The steward gave me an odd look, but said that he would mention it. Next, I was taken to meet Drusilla Gratiana.

The noble Drusilla was a typical senator's wife: an ordinary woman in her forties who, because she was descended from sixteen generations of senatorial stiffs, believed herself exceptional. The only thing that made her different from a fishwife slitting open fresh-caught mullet was her spending budget.

Drusilla Gratiana had papery skin, a suspicious expression, a twenty-five-thousand sesterces pearl necklace bestowed on her by Quadrumatus, four children of whom one daughter was betrothed last month, a troupe of pet dwarfs, a corn warehouse she inherited from her uncle, and a drink habit. Some of this I had extracted from the steward, the rest was obvious. She was draped in red-purple silk, which two pale maidens kept tidy while a seventy-year-old wardrobe mistress constantly supervised. My mother would have made a friend of this black-clad crone. Her contempt for me was immediate. I did not imagine the malignant attendant had seen Veleda as an ornament to the household either.

'We are expecting Cleander,' barked the wrinkled and beady-eyed creature. 'You'll have to be quick!'

I ignored her. I addressed her mistress direct in a cool, calm voice that was meant to establish my credentials as a man of refined manners. It irritated all the women in the room. 'Drusilla Gratiana, I offer my condolences on your brother's dreadful fate. I regret any disturbance I have to cause to your household. But I must confirm exactly what happened, so I can bring the perpetrator to justice.' 'As Phryne says: be quick then!' Mistress and maid worked as a team. Just my luck. 'Who is Cleander?' 'My lady's doctor.' I was told this by the black-clad Phryne, angrily of course.

The noble lady and her freedwoman were bound by thirty years of complicity. Phryne had decked out Drusilla Gratiana as a bride; she knew all her secrets, not least where she kept the wine flagon; there would be no bumping Phryne out of the way. She was owed too much. She wanted to control Drusilla; she would stick around.

I cleared my throat. 'I'll try to be brief, then… Were you close to your brother?'

'Of course.' Apart from the fact that Drusilla spoke rather dreamily, with a husky toper's voice, that told me nothing. Gratianus Scaeva could have lived with his sister because they were devoted or because he was a social liability who needed to be kept under tight control. The relationship between the siblings could have been anywhere on a spectrum between incest and outright loathing. Nobody intended me to find out. 'Yes, I assumed that – because he lived with you. Was he your only brother, by the way?' 'I have two others and two sisters. Scaeva happened to be unmarried.' So now I had it: of his five married brothers and sisters, Drusilla Gratiana had the richest spouse and the most comfortable home. Gratianus Scaeva knew how to sponge. 'Not found the right girl yet?' Drusilla gave me a nasty look. 'There was nothing wrong with him, if that is what you are implying! He was only twenty-five and perfectly normal, though not strong. He would have been a wonderful husband and father; all that has been taken away from him.' I won't say she cried. It would have spoiled her careful face makeup. Besides, I was a lout and she was too proud to give way.

I wished I had brought Helena Justina for this. Even the old bag in black would have been impressed by her.

'This is bound to be painful, but I need to ask about how you found your brother's head, please.' Drusilla Gratiana whimpered and looked faint. Phryne shuddered, making a big show of it. 'Was there any particular reason why you went into the atrium, or were you just passing through normally on your way somewhere?' With a struggle, Drusilla gave a slight nod that indicated the latter. 'I'm sorry. This is unacceptably hard for you. I won't ask you any more.'

I was only being amenable because my interview was ended anyway: the damned doctor had turned up. I knew who he was from the stuffed satchel of medicaments, the piqued frown, and the bustling manner that told his patients they were being charged by the minute by an exceptionally busy specialist who was much in demand. 'Who is this low fellow?' 'The name is Falco. Didius Falco.' 'You look like a slave.' His arrogance smelt like a fisherman's fart, but I was not in the mood for nit-picking.

Drusilla Gratiana was already stretching out on a couch. There were some female invalids with whom I would happily play doctors and nurses. In this case, I left. Some informers get to deal with buxom young female slaves who carry the titbit trays and yearn to make free with male visitors. My name is Didius Falco, and I end up with implacable old freedwomen: Cleander had shooed her out, making it plain that however intimate she was with Drusilla, he would not accept an underling at his consultation. I now needed to be shown where the torso was found and hoped to be led there by the house steward – but once she had been turfed out of the consultation, Phryne took over supervising me. 'What's wrong with your mistress?' I enquired as we walked. 'She suffers with her nerves.' 'And that was her doctor. What's his name again?' 'Cleander.' Phryne disliked him. In view of his snooty attitude towards her, it was understandable. 'He's a Greek?' 'He's a Hippocratic pneumatist.' Sounded like he was a charlatan. 'And does he attend the whole family? I thought Quadrumatus Labeo sees Pylaemenes?'

'Pylaemenes is his dream therapist. His doctor is Aedemon. He is an Egyptian,' said Phryne, who had grasped my line of questioning. 'An Alexandrian empiricist.' Another quack.

'Drusilla Gratiana said her brother was not strong. Who looked after him?' 'Mastarna. Etruscan. A dogmatist.'

As she grew more terse, I took the hint and kept quiet until we came to a prettily decorated salon. It must have been thoroughly cleaned up; there was no sign now of the reported pools of blood. Gratianus Scaeva had been found on a reading couch; it had since been replaced with a different one. There were goat-footed marble side tables, display cabinets with a selection of bronze miniatures, lampstands, a couple of cedarwood scroll boxes, rugs, cushions, a hot wine dispenser, pens and ink, and in short, more pieces of furniture and knick-knacks than my mother had in her whole house – but no clues.