`Who's Scythax?' I put in.

`A medico attached to our patrols.' The vigiles always had doctors on the squad; they looked after the patrolmen, whose work led to frequent injuries, and when there were bad fires or building collapses they tended civilian victims at the scene. `Falco, I think you and I should go to the victim's home. Martinus, if you are going to the station house, send a detachment to meet us at the Nonnius place. I'll have to search it, and probably guard it afterwards. Mind you, Rubella won't be happy to allow us the men…'

Mention of Rubella made me go quiet.

On the way to the Capena Gate we bought bread rolls and munched as we walked. Luckily sight of a corpse always stopped Petro wanting to talk. He must have assumed I was reacting the same way.

We strolled the length of the Circus on the north side, then around its end under the Appian and Marcian aqueducts. As we emerged from their shadow, shopkeepers were unlocking their booths and washing the pavements. There were some decent residential streets but they were interspersed with rougher ones. Interestingly, it was an area of mixed jurisdiction by the vigiles. The First region, which we were just entering, was looked after by the Fifth Cohort, yet we were quite near to the Twelfth region, which as part of the Aventine came under the Fourth. We were also very close to the much seedier quarter where Plato's Academy lurked. That was in the Circus Maximus region, the Eleventh, and like the Forum Boarium it was prowled by the Sixth Cohort.

`Petro, does the fact that three different groups of vigiles are responsible for this triangle have any bearing on the crime that's rife?'

`Probably,' he said. I could not tell him that according to Rubella criminality occurred amongst the vigiles themselves. `Do you work closely together?'

`Not if we can help it.'

`Any reason?' I was hoping there would be one.

`I've enough to do without wasting effort on "inter-cohort cooperation"!' Petro sneered.

`Strikes me the cohorts all have different characters?'

`Right. The Fifth are dull, the Sixth are bastards, and as you know, we in the Fourth are unsung heroes with a mature and efficient approach!'

I just hoped I could show that that was the truth.

I took a deep breath. `Are Tibullinus and Arica on the take?' `Probably,' said Petro shortly. Something in his manner made me reluctant to ask more.

As we neared the street we wanted, a familiar figure hailed me. `Marcus!'

'Quintus! I heard you were back from Germany. Oh this is good, Petro, let me introduce you to Camillus Justinus.'

Justinus was Helena's younger brother, a slight, boyish lad of twenty-odd. Today he was in civilian dress – a pristine white tunic and rather casually draped toga. The last time I saw him he had been in tribunal uniform, in the army on the Rhine. I myself had been there on a mission for Vespasian, one Justinus had joined in, acquitting himself bravely. I knew he had been recalled and was now expected to work through the stages of upper-class civilian life, probably ending in the Senate when he reached twenty-five. Despite that, I liked him. We embraced like brothers, and I chaffed him about his position.

`That's right. I've been brought back home to be a good boy, and to start planning to cadge votes.'

`Don't worry. The Senate's a doddle. All you have to do is learn to say, "Gods, what a stench!" every time you appear in a crowd, while keeping your teeth bared in a friendly smile in case any of the plebs can lip-read.'

`Well, it's a few years away yet…' Justinus sighed. `I was hoping to see you. I think I'm in love with an actress.'

Petro and I turned to one another and groaned.

`Why do the young always have to make the old mistakes?' I asked. Petro shook his head sadly. Petro and I had been friends with a few stage performers in our day, but now we had responsibilities. (We were too old, too cynical, and too careful with our cash.)

`I think you may know her -' Justinus tried.

`Very probably!' exclaimed Petronius, as if it was nothing to be proud of. Since getting married, he had turned highly self-righteous. I suspected it was a deliberate pose. He hadn't really changed.

'Quintus, don't ask me any favours to do with entertainers! I'm in enough trouble with your family.'

Justinus slipped into his infectious grin. `That's true – and heading for more! If I see you I am to invite you and Helena to dinner on her birthday. Tomorrow,' he spelt out annoyingly. That reminded me about my lost birthday present problem, and I cursed to myself. `What you don't know', continued Helena's favourite brother, `is that someone else has come home from abroad. Somebody who doesn't take kindly to having his sister living with an informer, and who keeps describing in tortuous detail what he would like to do to you.'

`Aelianus?'

`Aelianus.' The other brother, whom I had never met but already disliked. His views on me were plain too; he had written them to his sister with great acrimony. The distress he had caused Helena was more than I could think about.

`Looks as if we're heading for a wonderful evening!' I commented.

Quintus Camillus Justinus, an odd soul who happened to believe I was quite good for his sister, gave me a formal salute. `You can, of course, rely on my unstinted support, Marcus Didius!'

`Oh thanks!' I said.

He would make a good politician: it was a blatant bribe. So now I had to find time to introduce a senator's son to an actress, then watch him ruin his previously immaculate reputation in a scandalous love affair. No doubt afterwards I would be expected to help this young man tour the city trying to win votes.

Petronius and I were admitted to the Nonnius house by the porter as soon as we shouted our arrival. He seemed relieved that we had turned up to take charge. He came out to greet us carrying a temporary screen and watched us examine the front door, which had been battered open last night so efficiently that little of it now remained. `They came in a cart with a ram on it. A pointed tree trunk mounted on a frame. They pulled it back on a sling, then let go – it crashed right through.'

Petro and I winced. This was real siege warfare. No house in Rome would be safe from such artillery – and only a daring gang would risk taking that kind of illegal weapon openly through the streets.

The house was silent now. Nonnius had been unmarried and had no known relatives. With him gone, domestic management would come to a full stop.

We walked about unhindered, finding few of the slaves who had been in evidence the last time I visited. Maybe some had run away, either eager to be free or simply terrified. In strict law, when a man was murdered, his slaves were subjected to statutory torture to make them identify his murderer. Any who had denied him assistance would be punished severely. If he was murdered in his own house, his slaves were bound to be the first suspects.

The porter was the most helpful. He freely confessed that strange men had come to the house after dark, had broken down the door suddenly and violently, and rushed past him. He had hidden in his cubicle. Sometime later the men had left. A long time after that he had ventured out. He learned from the others that Nonnius had been dragged away.

None of the other slaves would admit to having seen what was done to their master. At last we found the little Negro who had been his personal attendant; the child was still hiding under a bedroom couch, crazy with fear. He must know the truth, but we got nothing from him but whimpering. Some of the cohort had turned up by then, brought here by Fusculus. Petronius, not unkindly, put the child in the charge of one of them and ordered him to be brought to the station house.