'I don't know-ow – Owl' He might be a spirit but he knew when his privates were kneed. This was my first time putting the persuaders on a ghost. His ectoplasm had more substance than he pretended. After a couple of wine cups, I was not gentle; my sudden jerk produced a satisfactory shriek.

'Stop messing about, or you'll really be dead and I won't bother to bury you.' I had no time for finesse. 'Look here – Members of my family, some of whom are young and sensitive, are gathering to see what's going on. I'll have to beat you up fast and very hard…' Zoilus understood. He had roamed among vagrants long enough to know about impatient men and the pain they could inflict.

He caved in and answered me sensibly. He knew about the runaways who died in the night even though they were fit, or halfway fit. I asked if he had seen any being killed. He moaned a bit, which I took for an affirmative. I asked if the killer was a woman or a man; to my surprise, he said a man. It was one of the few statements I had ever heard him make with firmness. 'Are you sure? So what had Zosime to do with it?' 'Woo-oo…' This tremor was barely audible. 'Oh stop it, Zoilus. Brace up, you ghoul! If I brought him in front of you, could you identify this man?'

But Zoilus collapsed. Hiding his head in his spectral robe, he just writhed about and moaned more. Eventually I foolishly loosened my hold on him as Junia interrupted again, bringing a tray of dubious looking bites. Zoilus made a sudden run for it, through a set of double doors and away across the home-built sun terrace that was the pride and joy of Gaius Baebius. My hands were too greasy to stop him; my will was flagging too. As he fled, he snatched the purse with his agreed fee from Junia, but ignored her snacks. Maybe he could tell that my sister's famous over-salted, under-spiced deep-fried sesame balls were as hard as Pluto's heart in Hades.

SATURNALIA, DAY SIX

Eleven days before the Kalends of January (22 December)

The sixth day of Saturn alia often sees revellers reviving. Those who had been out of their heads for the past five days either die of drink and debauchery or learn to live with their condition. I felt I was enduring the worst aspects, with no chance to enjoy myself I missed the good events because of my work, and was sober for the grim ones.

Junia's layered cheesecake was repeating on me acidically when I climbed out of bed. Helena rubbed my hunched shoulders and crooned sympathetically. 'I'm depressed about that flautist.' 'I know you are, love. Maybe today Mother will manage to get into the Vestals' House. She knows we are going to them tonight -' 'Are we?' 'I'm sure I told you, Marcus.' 'I'm sure you thought you did!' 'Oh please be good about it. Mother is trying to create a normal festival for Claudia. She will do her best for you; she realises you're bound to ask has she talked to Ganna.'

Being 'normal for Claudia' might be Julia Justa's aim, but her eccentric daughter threatened to jeopardise that: Helena had a bad conscience about leaving the priestess on her own for the past two evenings, so she proposed taking Veleda with us this time.

'That's risking trouble! Ulterior motive? – You think ifClaudia hits her hard enough, Veleda will be done for and my problem will be over?' 'Desperation! Somehow, Marcus, we have to resolve issues.' I said I wanted to resolve what I would have for breakfast first. It ended up being honey on a brown roll, but I ate it on the hoof Petronius Longus sent me a message to come to the doctor Mastarna's house. It wasn't to help Petro face up to a medical consultation: Scaeva's physician had killed himself I walked to the place by the Library of Pollio, musing on how many times I had been called out at first light by the vigiles. Suspicious deaths often occurred at night. Either that, or nosy neighbours informed at the patrol house last thing, so they could go to bed with a clear conscience. Sometimes the watch simply found the corpses while they did their rounds.

When I reached the house, processing was virtually complete. 'Your name came up,' Petro informed me dourly. Whenever he found me involved in a case, he disapproved.

What had happened looked obvious. Mastarna had been found by his housekeeper, the lop-sided midget I had seen before busying herself around his smart apartment. She was now pretty shocked. Sometimes if she had backache Mastarna would give her a 'tonic' so she slept well and the pain eased. She must have known that he had a habit of dosing himself with mandrake too, but she had not expected the jug of poison.

We know he did himself in,' Petronius confirmed. 'It's classic. He left a note.'

'Don't say that's where my name cropped up?'

'Bright boy. "There is no way out. Falco knows everything. I apologise." So what's that about?'

I sat down to think. His despair could be because I had announced yesterday that I was on the verge of identifying Scaeva's killer. Petro and I gazed at the Etruscan lying on his reading couch. The toga he had worn so fastidiously when Helena and I visited now lay in a crumpled heap on the floor, one of the signs that he had roamed about the room in anguish before he stretched out on his couch, with a jug of dark liquid. There was a clean cup on the tray, untouched. He had swigged straight from the jug. Then he tossed the valuable article across the room. Drips followed its progress. One of the vigiles rubbed at a spot on the floorboards; Petro kicked him just in time as he went to lick his finger and taste the stuff.

Petronius knew more than he had at first revealed, even to me. Mastarna had died yesterday evening. Before that, he had been visited by a colleague who had greatly upset him. The housekeeper was bad with names but she said the fellow-doctor was a Greek.

'Must be Cleander. He has a spiteful attitude. And he gave the impression he knew something- must have concerned Mastarna.'

There had been a short argument, then Cleander left. Mastarna went out a couple of times, seeming agitated and saying he wanted to seek advice from friends, but he returned forlorn because they were out. He asked for writing materials and sent the housekeeper to her own house; she lodged elsewhere. She said he was a very private man; Petro and I exchanged glances. Uneasy, the loyal biddy had got up very early and came to check on him. When she could get no answer, she panicked. Thinking the worst, she sent for the vigiles.

'One of his friends turned up to see what Mastarna wanted yesterday – apparently he went around banging on doors like mad. The fellow is co-operating.' Petro had closeted the witness in another room, to which he now took me.

I was surprised to see Pylaemenes. The dream therapist said that he had not known Mastarna well. He had been surprised that the man had been trying to see him so urgently last night. 'Bit of a shock Aedemon says Mastarna was after him too.' 'Y ou both know something that explains Mastarna's suicide?' 'Everybody knows,' Pylaemenes exclaimed. 'Mter we saw you yesterday, that bastard Cleander must have come here, crowing that the game was up – they were always on bad terms. Mastarna tried turning to Aedemon and me but then he despaired… Somebody is going to tell you now, so it may as well be me. This is what I know, Falco. I had a slight involvement because there had been a family argument. Quadrumatus needed me to interpret a dream and tell him whether he was right to take a stand.'

'Quadrumatus Labeo,' I told Petro, 'is a man of enormous wealth and power, apparently incisive – yet he can't jump unless this star-spangled Chaldean tells him what to do.' 'What was the problem?' Petro asked Pylaemenes. 'Scaeva. Scaeva was always sickly. He wanted to be well for Saturnalia, when they had a big programme of events planned. He and his sister -' 'Drusilla Gratiana. Wife to Quadrumatus,' I spelled out to Petro. 'They were keen that Mastarna should carry out an operation on Scaeva's throat. Mastarna claimed he could remove Scaeva's inflamed tonsils and cure him. But Quadrumatus has his own doctor Aedemon – who strongly warned against it. Aedemon wanted to purge the patient of the impurities that he said would be causing the infections. As you know Fako, Cleander attends on Drusilla; he also is a huge opponent of surgery – that's his beef against Mastarna. But Drusilla was dead set on her brother trying anything.' 'So young Scaeva is in misery, the doctors are all squabbling and the relatives are slogging it out at top volume; you get called in to tweak a dream or two as the beleaguered master's last resort?' Petronius looked askance. 'And you helped him decide what he thought, did you?' 'Quadrumatus forbade the surgery,' agreed Pylaemenes coolly. I saw it all now. 'The others ignored him? Mastarna egged on Scaeva; Scaeva and his sister secretly arranged to have it done. So what happened? Was the operation on the same day Scaeva was found dead?'