'Naturally!' Helena was wry. Once again, her right of complaint went unspoken: I was a thoughtless swine and she was supremely tolerant. In some homes, reaching this happy solution would require a large purchase of jewellery. I wiped away olive oil with my napkin then kissed her hand in a relaxed admission that I didn't deserve her. I kept hold of the hand temporarily, holding her long fingers against my cheek and considering just how lucky I was. A quiet moment passed between us. 'So tell me about it. What did Zosime want?' Helena pulled back her hand so she could pick at the dish of olives. They were small chewy black ones, marinated in garlic and chervil. 'She's a woman in her fifties, I'd say – once a nursing assistant, now calls herself a doctor, presumably experienced. She looks after female patients at the temple, ones who have gynaecological problems.' 'So was she called to see Veleda because the priestess had a complaint of that sort?' 'Well, Zosime says in her opinion Veleda had nothing like that at all and the Quadrumati sent for her because she was recommended by one of their other doctors. Veleda was suffering from some general illness, with bouts of fever and terrible headaches. In fact the pain was so bad, Veleda was begging for that terrifying surgery where people have a hole drilled in their skull -' 'Trepanation. ' 'Someone had told her a Roman surgeon could carry it out. Veleda had convinced herself it would relieve the pressure in her head.' Helena shuddered. 'It seems drastic. She must have felt desperate even though by then she knew she was doomed to die anyway.'

'There may be no escape from the public executioner, but patients have been known to survive trepanation,' I said. 'Many don't naturally, surgeons keep that quiet. What was Zosime's suggestion to help her?'

'Zosime works on gentle principles, what she calls "softly, safely, sweetly". It goes back to ancient Greek theories, the Hippocratic tradition, and involves treatments based on a combination of diet, exercise and rest. Zosime was not really given a chance to try this out, though. She prescribed a sensible regime, but was discouraged from visiting again.' I was startled. 'The Quadrumati locked her out?' 'Nothing so crude. But she took the hint and stopped attending.' 'Was Veleda happy with her?' 'Zosime thought so. But it was obvious to her that Veleda was not a tree agent.' 'Had Zosime been told that her patient was a prisoner?' 'Not directly.' 'You think she knew?' 'I think she's very shrewd,' Helena said. 'And could she have seen Veleda again, after Veleda escaped from the house?'

'Possibly. I didn't ask. How could I, without revealing things that are supposed to be kept secret?' This time, Helena's tone did contain a slight suggestion that the awkwardness of the mission was my fault.

'All right, go back a bit: why did Zosime think she had become unwelcome at the senator's house?'

'I had the impression there might have been conflict with one of the other doctors you told me are employed by the family. She muttered something about Mastarna, and used the phrase "damn fool dogmatist". I pressed her on that -' Helena could be stubborn in interrogations. She saw me smiling and threw an olive at me. I opened my mouth and it went straight in, for which I gloatingly took the credit. 'Well, your mouth's big enough, Falco!… It seems to have been Mastarna who was encouraging Veleda towards trepanation. Zosime was circumspect in talking to me – perhaps because she is a woman, venturing into what male doctors believe is their special territory – but it's clear she felt Mastarna had not bothered to carry out a proper diagnosis, but was dead set on radical surgery.'

I pondered this theory. 'Do you think that after Zosime left, this crazy knife-man persuaded Veleda to have the trepanation after all, that he drilled out a circle of her skull and managed to kill her with the procedure – so somebody has hidden her body to avoid political embarrassment?' 'Zosime did not suggest it.' 'If she stopped visiting the house, she wouldn't know. She may never have dealt with the kind of devious people we meet.' I was now thinking back to my interviews that morning with Quadrumatus Labeo and his wife, trying to decide whether they could have been hiding such a cover-up. 'Was Mastarna one of the doctors you met today?' Helena asked. 'No, I just saw the senator's dream therapist – Pylaemenes, a crackpot Chaldean – then I had a surly encounter with Cleander, who came to tickle up the wife with his cold Greek fingers.' 'You're being lewd, Marcus.' 'Who, me? Cleander once taught Greek theory to Zosime, but that doesn't make him enlightened; he's an arrogant swine who looks down on mere mortals. Presumably he's in medicine for the money, not from charitable feelings. I can't imagine he was connected to the Temple of Жsculapius for long. Now what else did the witchy freedwoman say – dark, forbidding Phryne – the senator has a tame Egyptian, who I suppose feeds him ground crocodile bones, and yes: then there's Mastarna – Mastarna, she told me, used to look after the dead man. So Gratianus Scaeva was in the hands of the keen surgeon Zosime quarrelled with.'

Helena slowly munched a slightly stale bread roll. I said she liked a challenge. I had seen her test her teeth on hard crusts before, in the same way that my mother always made out it was her maternal lot to endure leftovers and inedible scraps. 'So,' Helena asked me eventually, when her jaw tired of this punishment, 'what is the significance of Scaeva's doctor in this household of hypochondriacs?'

'The answer will probably depend,' I said, 'on whatever link we find between Veleda and Scaeva. Who really killed him: whether it was, or was not, Veleda. And why? Was there any connection between the death of Scaeva and the timing of Veleda's escape – other than her taking advantage of panic and commotion in the house?'

'His head was cut off,' Helena commented, in surprise. 'Are you suggesting that somebody other than Veleda carried out that particularly Celtic act?'

'Could be. I never saw the body; of course it's cremated. I'd like to ask Mastarna if he carried out a professional examination when his patient's corpse was found. There could have been other wounds, wounds that were inflicted first. Who would bother to check? There's a man with his head cut off, so you assume that is the cause of death… But I shall keep an open mind. He could have died some other way, then Veleda's presence in the house gave someone the idea to blame his death on her.'

'Somebody with a very cool nerve!' Helena commented. 'Even if Scaeva was already dead, I imagine it takes courage to decapitate a corpse. '

'You're right. The tribes do it in the heat of battle, and they do it to their enemies which must be an encouragement… Maybe, when I find an opportunity,' I said, 'I should find out what enemies Gratianus Scaeva had.' Helena pulled a face. 'He was a young man. Was he the type to have enemies?'

I laughed bitterly. 'Well born, well off, well thought of… I was told he was a perfect character – so trust me, fruit; he's bound to have been a right bastard!'