Frontinus asked the first question, and it was typically direct: `Do you have a map of the water system?'

`I believe a locational diagram of the, substrata and superstrata conduits may exist.'

Petronius caught my eye. His favourite: a man who called a spade a soil redistribution implement.

`Can you supply a copy?'

`Such classified information is not generally available'

`I see!' Frontinus glared. If he ever assumed a position administering water, we could tell who would be the first bad nut tossed out of the window.

`Perhaps, then,' suggested Petro, playing the sympathetic fraternal type (well, a big brother with a hard stick in his fist), `you could just tell us something about how things work?'

Statius had recourse to hiss satchel, wherein he had secreted a linen handkerchief to mop his brow. He was overweight and red in the face. His tunic crumpled around him in grubby-looking folds, even though it had probably been clean on that day. `Well, it is complicated to, explain to lay persons. What you are requesting is highly technical.

`Try me. How many aqueducts are there?'

'Eight,' admitted Statius, after a horrified pause.

`Nine, surely?' I ventured quietly.

He looked annoyed. `Well, if you're going to include the Alsietina -'

`Is there any reason why I should not?'

`It's on, the Transtiberina side.'

`I realise that.'

`The Aqua Alsietina is only used for the naumachia and for watering Caesar's Gardens

`Or, for the Transtiberina paupers to drink when the other aqueducts are dry.' I was annoyed. `We know the quality is filthy. It was only ever intended to fill the basin for mock trireme fights. That's not the point, Statius. Have any women's hands, or other parts of human corpses, been found in the Alsietina?'

`I have no precise information on that.' `Then you concede remains may be there?' `It could be a statistical possibility.'

`It's statistically certain that a watercourse somewhere is awash with heads, legs and arms too. Where there are hands the rest of the set tends to exist – and we haven't found any of them yet.'

Petronius weighed in again, still complementing me by playing the kind-hearted reasonable type: `Well, shall we call the tally nine? With luck some can be eliminated fairly quickly, but we must start by considering the whole system. We have to decide how a man, and his accomplices if he has any, are taking advantage of the aqueducts to flush away the relics of their hideous crimes.'

Statius was still bound up in irrelevance. `The water board accepts no responsibility for that. You cannot be suggesting that the notoriously unpleasant quality of the Aqua Alsietina is accounted for by illegal impurities of human origin?'

`Of course not,' said Petro grimly.

`Of course not,' I agreed. `The Alsietina is full of perfectly natural crap.'

The engineer's eyes, which were too close together, fluttered nervously between us. He knew Julius Frontinus was too important to despise, but he saw us as unpleasant insects he would like to swat if he dared. `You are trying to trace how a few – a relatively few – undesirable remains have been introduced to the channels. Well, I sympathise with the initiative ' He was lying. `But we have to appreciate the magnitude of scale impeding us At least he was talking.

We listened in silence. He had somehow gained confidence; maybe refusing requests made him feel big. `The freshwater installation comprises between two and three hundred miles of channel ' That seemed a very vague calculation. Somebody must have measured more accurately, at the very least when the aqueducts were built. `I am given to understand that these extraordinary pollutants -

`Limbs,' stated Petronius.

`Have been manifesting themselves in the water towers – of which the system is provided with a daunting multitude Frontinus demanded immediately, `How many?',

Statius consulted his assistant, who readily informed us, `The Aqua Claudia and Anio Novus together have nearly a hundred castelli, and for the whole system you could more than double that '

I noticed that Frontinus' was jotting down the figures. He did it himself, not using a scribe though he must own plenty. `What's the daily, water discharge?' he barked. Statius blenched. 'Roughly,' Frontinus added helpfully.

Again Statius needed the assistant, who said matter of factly: `It's difficult to measure because the currents are constantly flowing and also there are seasonal variations: I roughed up some statistics once for the Aqua Claudia, one of the big four from the Sabine Hills. It was mind-boggling, sir. We managed to do some technical measurements, and when I extrapolated the figures I reckoned on a daily delivery of something, over seven million cubic feet. Call it, in everyday terms, going on for seven million standard amphorae – or by the culleus, if you prefer, over sixty thousand.'

Since a culleus is one great mountain of a cartload, sixty thousand rolling up full of water was indeed hard to imagine. And that was only the quantity delivered to Rome by a single aqueduct in one day.

`Is it relevant?' asked Statius. Far from being grateful, he seemed annoyed at being shown, up by a subordinate.

Frontinus looked up, still round-eyed from the figures. `I have no idea, yet. But it's fascinating.'

`What nobody knows,' continued the assistant, who was rather enjoying himself, `is whether any human remains arelying undiscovered in the settling tanks along the route.'

`How many tanks are there?' asked Petro, jumping in before the intrigued Consul could beat him to it.

`Innumerable.' Statius supplied the put-down crisply for himself The assistant looked as if he knew the real answer, but he kept quiet.

`You can take a census and count them now,' growled Frontinus to the senior engineer. `I understand this revolting contamination has been happening for years. I am astonished the water board has not investigated long ago.'

He paused, obviously expecting an explanation, but Statius failed to take the hint. Petro and I were witching a head-on clash between intelligence and stodge. The ex-Consul had all the flair and quickness that shines in the best administrators; the engineer had floated up through a corrupt agency by virtue of just sitting back and putting the seal on whatever his underlings passed to him. Neither man could quite believe the other specimen existed.

Frontinus saw he had to be firm. `Vespasian intends this dreadful business to be stopped. I shall instruct the Curator to have all the castelli searched immediately – then you must start working through all the settling tanks as quickly as possible. The victims need to be found, identified and given reverent funerals.'

`I understood they were assumed only to be slaves,' Statius, still resisting, said feebly.

There was a pause.

`They probably arc,' agreed Petronius. His tone was dry. `So this is all a waste of resources as well as a risk to public health.'

The engineer wisely made no reply. We could hear echoing in his silence all the mockery and obscenity that must have greeted each new ghastly discovery by the aqueduct workers over the years, and the groans of their superiors as they planned how to cover it up. Helena had been right: these deaths were seen as an inconvenience. Even the formal commission that might stop them was an irritation imposed unfairly from above.

Julius Frontinus glanced at Petro and me. `Any further questions?' He was making, it no secret that he had had enough of. Statius and his non-committal verbiage. We shook our heads.

As the engineer's party was leaving, I collared the assistant's chubby clerk. I had brought out a note-tablet and a stylus, and asked him for his name as if I had been deputed to take minutes of the meeting and needed to concoct the normal list of persons present to fill up my scroll. He confided his cognomen as if it were a state secret, `And who's the Assistant?'