I whistled. `Someone should hand out warnings to innocent travellers! But how did you prove it? Surely the brothel's mother hen was used to denying all knowledge of trouble?'

`Oh yes. Lalage's well up to it. I'd never have pinned her down, and. I'm not sure I'd even have fancied tackling her… Thank Jupiter Plato's is on the Sixth Cohort's beat, and I don't normally have the problem.' I saw his point. The whores who crowded around the Circus Maximus were as fierce as lynxes, and Lalage,.the madam at Plato's, had a phenomenal reputation. `There was a witness,' Petro told me grimly. 'And for the first time in history it was a witness who managed not to yell at the scene of the crime. So instead of the usual turn-up where the witness gets stabbed too, he hid up in the rafters until he had a chance to run away.'

`Unbelievable.'

`Better yet, one of my men then found him wandering in shock up on the Hill. He blurted out his tale, and we went straight to Plato's. The Sixth were nowhere in sight – that's normal – so we handled it ourselves. We were able to jump from an alley just as two bouncers were dragging the corpse out through the back door. That pegged the crime to the brothel. So for a start, when we went into court half the Thirteenth sector Watch had seen Plato's management towing the Lycian to a gutter by the boot-thongs, with Lalage herself holding a lamp. Next we had our witness to narrate the stabbing luridly. He was a second Lycian who had been smuggled in by the first one. The pair were hoping to slip the girl a copper and get a double spike half-price.'

I slapped the table. `Disgraceful! How can you police the city when even the victims are crooks?'

`Falco, I'll live with it! I locked our witness in protective custody, lost the address until he was needed, then produced him at the Basilica in his best tunic to tell how he had trembled in his hiding place and seen all. He identified the prostitute, the madam, and the creeping snatch.'

`Do I know the snatch?'

`A weasel called Castus.'

It meant nothing. I didn't ask if I knew the prostitute, and Petro didn't bother to embarrass anyone by naming her. `So what about your star witness? What about Nonnius?'

`We were well set up by the time our barrister called him. All Nonnius Albius had to do was to confess his own role as a Balbinus collector, and state that he knew the killer Castus was on the Balbinus payroll. He played his part very prettily – he even produced tallies to show the percentage Balbinus regularly took from stolen purses at the brothel.'

`Good value!'

`A prime witness. Our Lycian had come up with some joyful clinchers, like Castus exclaiming as he stabbed the dead man, "Teach him to argue with Balbinus!" Nonnius then told the jury that all the Balbinus henchmen are routinely ordered to slash if trouble threatens. He had frequently heard Balbinus give those instructions. So we had him for organised crime, profiteering, and conspiracy, resulting in actual death.'

`The jury bought it?'

`Marponius had explained to them that he needed their cooperation if he was to be seen as the judge who cleaned up Rome.

Marponius was the main judge in the murder court. He was keen on his work, and personally ambitious, though not necessarily as blatant as Petronius made out. For one thing, Marponius was not a clever man.

`There were some juicy details,' Petro said. `I was threatening Lalage with a range of offences against the prostitutes' registration rules, so even she went into court to give evidence on our side.'

`Couldn't Balbinus buy her off?'

`I reckon she's keen to see him take a trip,' opined Petronius. `Lalage would be quite capable of running Plato's on her own. Maybe things were different once, but nowadays she really doesn't need a king of crime creaming off the top of her income.' He leant back and went on with his usual modesty: `Oh I had some luck in the timing. Balbinus believed himself untouchable, but there was a new mood in the underworld. People were ready to revolt. I noticed the change before he did, that's all.'

The point was, Petronius Longus had noticed. Many an enquiry captain would have had his nose so close to the pavings he wouldn't have spotted the flies on the balcony.

`Take your credit for sniffing the air,' I commanded. `And then for fixing it!'

He smiled quietly.

`So your jury convicted, and Marponius did his own career some good by handing out a death penalty – I presume the Assembly ratified the sentence. Did Balbinus appeal any further?'

`Straight to Vespasian – and it came straight back negative.'

`That's something!' I commented. We were both cynics about the Establishment. `Who signed the chitty?'

`Titus.'

`Vespasian must have approved.'

`Oh yes.' Only the Emperor has the final power of removing life from a Roman citizen, even if the citizen's life smells like a pile of cat's turds. `I was quite impressed by the quick response,' Petro admitted. `I don't really know whether Balbinus offered money to officials, but if he tried it he was wasting his time. Things at the Palace seem to be scented like Paestum violets nowadays.' One good result of the new Flavian Caesars. Graft had gone over the balcony with Nero, apparently. Petro seemed confident anyway. `Well it was the result I wanted, so that's that.'

`Here we are!' I congratulated him. `Ostia at dawn!'

`Ostia,' he agreed, perhaps more cautiously. `Marponius gets a free meal at the Palace; I get a scroll with a friendly message from Titus Caesar; the underworld gets a warning-'

`And Balbinus?'

`Balbinus,' growled Petronius Longus bitterly, `gets time to depart.'

I SUPPOSE IT is a comfort to us all we who carry the privilege of being full citizens of the Empire – to know that except in times of extreme political chaos when civilisation is dispensed with, we can do what we like yet remain untouchable.

It is, of course, a crime for any of us to profiteer while on foreign service; commit parricide; rape a vestal virgin; conspire to assassinate the Emperor; fornicate with another man's slave; or let amphorae drop off our balconies so as to dent fellow citizens' heads. For such evil deeds we can be prosecuted by any righteous free man who is prepared to pay a barrister. We can be invited before a praetor for an embarrassing discussion. If the praetor hates our face, or merely disbelieves our story, we can be sent to trial, and if the jury hates us too we can be convicted. For the worst crimes we can be sentenced to a short social meeting with the public strangler. But, freedom being an inalienable and perpetual state, we cannot be made to endure imprisonment. So while the public strangler is looking up a blank date in his calender, we can wave him goodbye.

In the days of Sulla so many criminals were skipping punishment, and it was obviously so cheap to operate, that finally the law enshrined this neat dictum: no Roman citizen who was sentenced to the death penalty might be arrested, even after the verdict, until he had been given time to depart. It was my right; it was Petro's right; and it was the right of the murderous Balbinus Pius to pack a few bags, assume a smug grin, and flee.

The point is supposed to be that living outside the Empire is, for a citizen, a penalty as savage as death. Balbinus must be quaking. Whoever thought that one up was not a travelling man. I had been outside the Empire, so my verdict was not quite that of a jurist. Outside the Empire can be perfectly liveable. Like anywhere, all you need to survive comfortably is slightly more cash than the natives. The sort of criminals who can afford the fare in the first place need have no qualms.

So here we were. Petronius Longus had convicted this mobster of heinous crimes and placed him under sentence of death – but he was not allowed to apply a manacle. Today had been set for the, execution. So this morning, while the greybeards from the Senate were tutting away over the decay of public order, Balbinus Pius would stroll out of Rome like a lord and set off for some hideaway. Presumably he had already filled it with golden chalices, with rich Falernian to slosh into them, and with fancy women to smile at him as they poured the happy grape. Petro could do nothing except make damn sure the bastard went.