Claudia's voice was dull. I had to bend forward to catch what she was saying. 'If this had never happened, we might have managed. If she had stayed in the forest, we might have been all right. I thought Quintus and I had remained friends through all our problems. We were bound to one another by love for our son.' Tears wound their way down her pale cheeks, unheeded. I hate to see a tough woman demoralised. 'It is no use,' she whispered. 'He has gone to her. I cannot hold him any longer. I have lost him now.'

Why is it that bad behaviour by one male gets all the rest of us into trouble?

Both Helena and her mother were polite women but strong-willed. They told me that I was expected to find Justinus, and I heard myself promising to do it. Unless he was already with Veleda, I really wanted him to stay missing. Keeping them apart was my best chance. If Justinus learned of my search for the priestess, he would attach himself to me – and not with a view to solving problems diplomatically. He would use me to find his forest sprite – and I knew he wouldn't be intending to give her back to the authorities.

My aim was to hand her in immediately. That is, immediately I had ascertained whether she did hack off the head of Quadrumatus' brother-in-law. That niggled me. It was not in character. And I owed her something for saving my life. If Veleda had not killed Scaeva, I would not let the authorities – or Scaeva's family – dump the crime on her just because it was convenient.

According to Claudia, Justinus had denied making any contact with the priestess since she came to Rome. If that was true – and he was usually too transparent to lie – then as far as I could see, there had been no opportunity for the pair to collude before Veleda did her flit, and little opportunity since. Without a pre-arranged rendezvous, she would never find him. And now he had vanished from home, she had no hope of fixing such a rendezvous. Or so I hoped. Maybe they had found one another and were now together? No. Not feasible. Not unless they had already been in contact somehow.

Never mind where Veleda had gone – where had he gone? Why had he gone? The element that made no sense was his buying a present for Claudia, as if he intended to crawl back home apologetically.

Could he have run into the priestess among the monuments south of the SaeptaJulia as he made his way home, and they had done a bunk? No. Too much of a coincidence.

A cynic might have suggested he had actually bought the gift for Veleda, to reinstate himself – but Pa would have sniffed out a subterfuge. Pa thought it was a genuine peace offering. Justinus had been horrified at hitting Claudia. Besides, when he and Veleda had been together in the forest, it was love's young dream; their relationship was far too ethereal to include the kind of bribery husbands and wives adopt in daily life. If Justinus went rushing to Veleda, he would fly headlong on swans down wings of love, without any basic planning.

I sent one of my nephews to obtain from my father a description of the purchased gift. Gaius, the runner, was also to tell Pa to ask around among his cronies at the Saepta and the Emporium for sightings of the missing man. Or indeed, sightings of the gift. Pa would love this. He adored pretending he was some kind of expert with a brilliant set of contacts, whereas I was an incompetent amateur. If he discovered anything, I would have to endure his crowing, but there was just a chance Pa would come up with results.

At home the pressure was truly on. In search of peace, I myself went to a wine bar up on the Aventine. I did not expect to find Justinus in this bolthole. As a place to drink it held very few attractions. But the waiter was amiable and the clientele, many of whom had something to hide from wives, mothers or taxation officials, respected other people's privacy. Until the First Adiutrix soldiers discovered it – as they were bound to – I could brood there alone.

Well, I took the dog. Walking Nux was always a good excuse to get out of the house. Flora's Caupona was no longer run by Flora, who had died, probably worn out by twenty years of living with my father. Previously given by Pa to this mistress of his as a little business where she could earn hairpin money (a business which kept her busy when she might otherwise have taken unwelcome interest in what he was up to), for about twelve months now Flora's had had my elder sister Junia as its hopeless proprietress. In the evening Junia was safe at home with her aggravating husband and her rather sweet deaf son; every day at sundown she would leave the caupona in the capable hands of the waiter, Apollonius, then everyone relaxed.

The bar was situated on a corner, as the best bars are. It had the usual two counters with crazy-marble tops, into which were set big pots containing sinister stews in anaemic hues, thickened with what seemed to be a mix of lentils and pavement dust. As the lukewarm pots fermented, from time to time half a gherkin or a lump of turnip would pop up through the slime, then softly sink to its death.

Awnings provided shelter in winter, when most topers sat miserably inside at a couple of wonky tables. Three wormy shelves on a wall held earthenware beakers. A clutch of amphorae leaned askew beneath them, around the bottom points of which Stringy, the caupona cat, curled his emaciated body. Stringy's diet, being the food at Flora's, was slowly poisoning him. The waiter (who always ate at the other caupona, the one across the street) either presided with lugubrious formality or lurked in a back room, where I knew he often read Euripides. When that happened it was bad news. He went off into another world and nobody could get served.

Tonight Apollonius was out among the clients, with a cloth over one arm. I had known him since he was an infant teacher; as a wine-bar waiter he still applied his skills to quell rowdies and to explain simple arithmetic to confused people who could not work out whether he had diddled their change. As I arrived that night, he was telling a drunken vegetable stall holder, 'I think we've all heard enough from you. Sit back on the bench and behave!' I felt I was seven years old again. The drunk did as he was told. I hid a smile.

Apollonius greeted me with a silent nod, then provided a dish of seeping chickpeas, which I ignored, and a cup of red wine, which I tried. 'I'd like your opinion of that, Marcus Didius.'

I noticed that instead of the normal thin crowd, tonight Flora's was warm and full of customers – all crushed in, hoping for free samples. The rest of them eyed me jealously. 'Junia experimenting with a new house wine?' I took a longer swig. 'Oddly enough, I can't taste anything wrong with it.' 'Oh it's not for here,' Apollonius hastened to calm my unease.

'That's reassuring. This caupona has a proud reputation for serving only the most disgusting rotgut on the Hill. People like to know where they stand, Apollonius. Change for change's sake is never welcome!'

Apollonius beamed. He had a quiet, intelligent sense of humour. This is always refreshing (and unexpected) in an intellectual. 'Trust me. We have no intention of destroying the traditions of the establishment. Rotgut remains the house speciality.' 'So what slippery travelling salesman offloaded this palatable gem on my dear sister?' 'We are testing it on a few favoured customers. Junia plans to provide this wine for the vigiles, at the Fourth Cohort's annual Saturnalia drinks party next week. She has been awarded the much coveted contract as their official caterer.' I whistled. 'What kind of bribe did that take?' 'I believe their tribune was impressed by her prospectus and sample menus,' returned Apollonius stiffly. He had a certain loyalty to Junia, as his employer, and managed to remain civil even after I guffawed. 'So what do you think, Falco?' 'I think it's all right.' He took the hint and gave me more. 'It's called Primitivum.' The vigiles would like that. I quaffed a couple of drinks, then prepared to go home.