Petronius Longus caught up with us that same evening.

We had been on the verge of turning in. Ma usually went to bed early, because at her age she needed to build up her stamina for the next day of furiously organising the family. She had waited up for our return-one of the restrictive practices that made me prefer to live elsewhere. After dinner at the Senator's I had chosen to come home, partly to reassure Ma but also because I knew if I stayed, as Helena's father offered (though her mother was markedly cooler), the Capena Gate house steward would give Helena and me separate rooms and I could not face a night of creeping along strange corridors trying to find my lass. I told Helena she could stay behind in comfort. 'They'll give you a softer pillow-'

She thumped my shoulder. 'That's the pillow I want.' So we both came back, which made two mothers happy-or as happy as mothers ever like to feel.

When they saw Petro shambling into the kitchen even Ma and Helena decided to stay up longer. Women took to him. If they had known as much about him as I did they might have been more disapproving; then again, they would probably have blamed me for the wild episodes in his past. For some reason Petro was a man whose indiscretions women excused. For some other reason, I was not.

He was thirty years old. He arrived dressed in various shapeless brown woollen garments, his usual unobtrusive working uniform, plus winter additions of fur in his boots and a hooded cloak so voluminous he could have been hiding three loose women and their pet duck under it. Stuck through his belt he carried a thick cudgel for encouraging quiet behaviour on the streets; these he supervised with a light, reasonable hand, backed up by well-aimed bodyweight. A twisted headband rumpled the straight brown hair on his broad head. He had a placid mentality he certainly needed when picking through the grime and greed at the low end of Roman society. He looked solid and tough, and good at his job-all of which he was. He was also a deeply sentimental family man-a thoroughly decent type.

I grinned widely. 'Now I know I'm really back in Rome!'

Petronius slowly lowered his large frame on to a bench. His expression was sheepish-presumably because he had a wine amphora under one arm, the usual credential he offered when visiting me.

'You look tired out,' Helena commented.

'I am.' He never wasted words. I cracked the wax of his amphora to save him the effort, then Ma produced winecups. He poured. He sloshed the liquor into the beakers with careless desperation, paused briefly to chink his cup on mine, then drank fast. He had trouble written all over him.

'Problems?' I asked.

'Nothing unusual.' Ma topped him up, then found a loaf and some olives to cosset him with. Petro was another friend of mine who was reckoned to be a cut above what I deserved. He rubbed his forehead wearily. 'Some tourist who managed to get himself slashed to ribbons by a maniac, or several, in a hired room: I can't say he should have used the door-bolt, because in that fleapit so much luxury wasn't available.'

'What was the motive? Robbery?'

'Could be.' Petro sounded terse.

In winter the rate of muggings among strangers usually fell. Professional thieves were too busy counting their winnings from the summer season. Actually killing the victim was a rare event. It attracted attention, and was normally unnecessary; there were pickings enough from idiots who came to see Rome, their pouches bursting with spending money, and then stood around the Via Sacra like curly little lambs waiting to be fleeced.

'Any clues?' I asked, trying to encourage him.

'Not sure. If there are, I don't like them. They made a disgusting mess. Blood everywhere.' He fell silent, as if he could not bear to talk about it.

Helena and Ma came to a mystical decision. They both yawned, patted Petro on the shoulder, ignored me, and made themselves scarce.

Petronius and I drank some more. The mood relaxed-or I assumed it did. We had known each other a long time. We had been best friends throughout our army careers; those had both been short (we helped each other fake reasons for leaving), but the province we had been allocated to was Britain, during a fairly lively period. Not something to forget.

'So how was the famous German trip, Falco?'

I told him something about it, though saved the best; his mind was clearly unreceptive to anecdotes. I saw no point in enduring the mishaps of travel and the trials of dealing with foreigners unless I could entertain my friends with them afterwards. 'Gaul seems as lousy as we remember it.'

'So when did you get back to Rome?'

'Day before yesterday.'

'I must have missed you around-been busy?'

'Nothing special.'

'I was looking for you earlier today.'

'Lenia told me.'

'So where were you?' Petro had a stolid insistence when he wanted to exert himself.

'I told you-nowhere special!' I was laughing at him cheerfully. 'Listen, you curious bastard, this conversation seems to be taking an odd tone. If I was a provincial sightseer you had stopped on the Via Ostiana, I'd be frightened you were going to demand a peek at my docket of citizenship on pain of five hours in your lock up: What's the game, Petro?'

'I wondered what you were up to this morning.'

I was still grinning. 'That sounds as if I need to consider it carefully. Jupiter, I hope I'm not being asked to produce an alibi.'

'Just tell me,' Petronius insisted.

'Bumming about. What else would I be doing? I've just come home after a foreign trip. I need to assert my effervescent presence on the streets of home.'

'Who saw you?' he asked quietly.

That was when I first realised the inquisition must be serious.

'What's up, Petro?' I heard my own voice drop several tones.

'Just answer the question.'

'There's no way I'm going to co-operate with a legal officer-any officer, Petro-unless I know why he's latched on to me.'

'It's better if you answer first.'

'Oh rot!'

'Not at all!' Petro was growing heated now. 'Listen, Falco, you've placed me between Scylla and Charybdis-and I'm in a very flimsy boat! I'm trying to help you; that ought to be obvious. Tell me where in Hades you were all morning, and make it good. You need to satisfy Marponius as well as me.' Marponius was a judge on the murder panel whose aegis included the Aventine. He was an interfering halfwit whom Petro could hardly tolerate; that was usual with officialdom.

'Right!' Anxiety made me speak angrily. 'Try this. This evening Helena and I gorged ourselves with luxury at the home of the most excellent Camillus. Presumably His Honour's word will be acceptable? You know Glaucus; Glaucus is straight. I was in the Forum; I saw my banker and Sattoria, not to mention Famia and Gaius Baebius, but I made sure they didn't see me, so that's no help. Perhaps they noticed me skulking behind a pillar, trying to avoid them,' I added with increased restraint, since Petro was looking at me mournfully.

'Who's Sattoria?' he asked, having recognised the other names.

'No one you know. No one I know any longer.' Not now I had a respectable girlfriend who took a sombre view of my bachelor past. Nice to have somebody bother about you. Nice, but occasionally things grew tense.

'Oh her!' Petro commented matter-of-factly. Sometimes I wondered about him. He looked henpecked, but occasionally gave the impression that he led a double life.

'You're bluffing, you beggar. You've no connection with Sattoria: After that I was up at the Palace for an hour or two, so surely even Marponius will say I'm in the clear for that period-'

'Skip the Palace. I've already covered that angle.' I was amazed. The sneaky bug must have been sleuthing round Rome as tenaciously as a clerk after promotion. 'I want your whereabouts earlier on.'