This seemed an educational spot for Petronius and me to bring young Larius. Having Venus as their patroness, the town councillors wanted her to feel at home. Once they rebuilt her own Temple it would dominate the Marine Gate, but she hardly needed that. The fashionable marker for every Pompeian's elegant vestibule was a wall painting of Priapus with his tireless erection; the richer they were, the more immense the welcome the god of procreation extended at their door. It was none too easy for strangers to distinguish the commercial brothels from private homes. (Judging by the town's racy reputation, it might not matter if you got it wrong.)

Spotting my nephew staring about with his sweet air of astonishment, a prostitute outside a genuine bordello grinned at him through her few blackened teeth. 'Hello, sonny! Want to meet a pretty girl?'

In a chalk sketch on their wall the lord of fertility, visibly virile yet again, demonstrated what was required of a lad, though the madam did not inspire much confidence. She was quite revolting under the clogging layers of kohl.

'We're just looking round at the moment,' I apologized sociably as Larius dodged back under my wing. 'Sorry, grandma-' For some reason the old bag of bones started shrieking abuse. Petronius grew flustered so we dived into the safety of an open-air winery.

'Don't expect me to lead you into bad ways,' I muttered to Larius. 'Your ma thinks I'm looking after you. Ask your father when you get home.'

My sister Galla's husband was a lazy river boatman whose main advantage was the fact he was never at home. He was a hopeless womanizer. We could all have coped if my sister had not minded, but Galla was unusually fastidious and she did. Sometimes he left her; more often Galla threw him out. Occasionally she relented 'for the sake of the children' (that tired old myth); the family's father stayed with her a month if she was lucky, then he drifted off after his next short-sighted garlandseller, my sister produced another unhappy baby, and the whole brood were left on their own again; when they were stuck, the poor things were sent to me.

Larius was looking morose as usual. I could not decide if it was being stuck, or being sent to me.

'Cheer up!' I chivvied. 'If you want to waste your pocket money ask Petro what to pay. He's a man of the world-'

'I'm happily married!' Petronius protested-though he then revealed to my nephew that he understood a fairly basic service could be had for a copper as.

'I wish,' Larius pronounced haughtily, 'people would stop ordering me to cheer up!' He stalked off to lean over the fountain at the crossroads, scooping up an abstemious drink of water by himself. A pimp spoke to him and he scuttled back; Petro and I pretended we had not seen.

I leaned on the counter with my nose in my beaker, facing up to the fact that I had half a score of nephews, of whom Galla's gloomy Larius was only the first to throw off his boyhood tunic at fourteen. Thanks to my own elusive father, I was acting head of our family. Here was I, meddling with high politics, scouring the coast for a renegade, dodging a murderer, booted into oblivion by the woman I had set my heart on-yet I had also promised my sister that sometime during this trip I would enlighten her boy on whichever facts of life he had failed to pick up already from his dreadful friends at school… Petronius Longus is always kind to a man in a crisis; he clapped me on the shoulder and treated us by paying for the wine.

As we went out I found myself glancing behind, afraid I might be followed by a grim wraith in a green cloak.

We had come to meet a man. As usual in these circumstances we suspected he would lead us a merry dance then rob us blind. Since he was a plumber, it was a virtual certainty.

We found our way north past the Temple of Fortuna Augustus towards the water tower beside the Vesuvius Gate. The Pompeians provided sensible raised walkways but at the hour we turned up they were using all the pavement space themselves, so we three honest strangers tramped through their rubbish in the road. While we concentrated on planting our sandals out of the stickiest mule dung it was difficult to inspect the street scenery, but from the back alleys we could glimpse the tops of trellises and walnut trees above high garden walls. Fine, spacious, two-storeyed houses faced onto the main thoroughfares, though there seemed to be a depression: so many were being converted into laundries and warehouses or let out piecemeal as apartments over shops.

Until the earthquake, the town's water system had relied on the aqueduct which brought water from Serinum to Neapolis, a handsome artefact with a subsidiary branch which came in here to a big square tower which had three arches of brickwork decorating its outer walls. Large mains used to lead off, one for the public fountains and two others for business premises and private homes, but the quake had cracked the cistern and broken up the distribution pipes. The man we wanted was tinkering with the reservoir half-heartedly. He wore the usual one-sleeved workman's tunic, two little warts beside his chin, and the whimsical, slightly tired expression of a man who is much brighter than his job requires.

'Been at it long?' I asked, trying to hide my amazement that in the country it took eight years to cement a leaky tank.

'Still waiting for a town-council order.' He clanked down his basket of chisels and wrenches. 'If you're buying a house in Pompeii, sink a deep well in your garden and pray for rain.'

I owed our introduction to my brother-in-law the plasterer; it took the form of that death's head phrase, Just mention my name… His name was Mico. I mentioned it extremely cautiously.

'Mico's name,' I admitted, 'sends even hard-bitten foremen with thirty years' experience rushing off to the nearest fountain to drown themselves-I dare say you remember him?'

'Oh, I remember Mico!' observed the plumber, through gritted teeth.

'I reckon,' suggested Petronius, who knew my cack-handed brother-in-law and despised him as we all did, 'that after enduring a riot and an earthquake, being visited by young Mico proves the proverb that disasters come in threes!'

Mico's plumber, whose name was Ventriculus, was a quiet, calm, honest-looking type who managed to give the impression that if he said you needed a new cistern it might almost be true. 'He was pretty bad,' agreed the plumber.

'Torture!' I said, starting to smile for the first time this trip. Heaping abuse on my brothers-in-law always cheers me up. 'A painter in Latium lost an eye when his brush bounced off a tumulus in Mico's bumpy skim. He received no compensation; the judge said, if he knew he was following Mico round he should have been prepared for hummocks…' I stopped, then we all grinned. 'So you're a friend of Mico's?'

'Isn't everyone?' murmured Ventriculus, and we all grinned again. Mico is convinced anyone who meets him loves him. The fact is, they just stand there trapped by his awful great-heartedness while he buys them drinks (he does buy the drinks-he buys plenty; once Mico gets you stuck in a tavern he keeps you squirming there for hours). 'Why,' Ventriculus teased me, 'would any loving brother give his sister to this Mico?'

'My sister Victorina gave herself!'

I could have added that she gave herself to anyone with the bad taste to have her, usually behind the Temple of Venus on the Aventine, but that cast a slur on the rest of the family which we did not deserve.

The thought of my relations was upsetting me so badly that I launched into what I wanted Ventriculus to do. He listened with the mild demeanour of a man who had waited eight years for his town council to draw up a specification for emergency repairs. 'We do have spare capacity; I can take on a foreigner…'