Starting near the city, we began a systematic search through the great variety of monuments. Most were close to the road, giving easy access for funerals, though space was tight and some had had to be built at a distance from the highway. Round ones were favourite but rectangles and pyramids were there too. They came in all designs, some small and low but many higher than a man or two-storied, with a lower chamber for the dead and an upstairs for the family to hold feasts. They were in weathered grey stone or different coloured brick. Some were in the form of ovens or pottery kilns, indicating the trades of their dead owners. Classical architecture, pilasters and porticos marked the resting places of cultural snobs; no doubt the urns that contained their burnt relics were of fine marble, carved alabaster or porphyry. Some tombs had religious decorations; others carried statues or busts of the deceased, sometimes accompanied by one of the gods.

Clemens found the first remains of a campsite. Blackened undergrowth showed where a small open-air fire had once been, probably for days on end. The ashes were cold. Broken amphora shards and a sodden old blanket with a distinctive smell convinced us this was not simply the remains of a formal cremation or of a family memorial party held outside a mausoleum. We continued searching and gradually came across more indications that Petro was correct. Locked chambers had had unpleasant rubbish deposited around them, especially in the entrance area. Ancient tombs which were no longer visited by relatives of the dead and newer ones with the doors recently broken in contained evidence of rough sleepers. Some had been used as lavatories. The worst were sordid after being used for both.

Starting to recognise the signs, we trod carefully near doorways. We held our breath before stooping to look inside open tombs. We poked at discarded clutter only with sticks, and we held the sticks at ann's length. We were wary of enclosures where rats might be foraging.

Clemens made the first sighting. He called out, and pointed to a thin figure, some way off, loping away from us. It was probably a man, dressed in patches, hunched double and carrying a bag of some sort over one shoulder. Whether or not he heard us shout, he kept going and was too far off for us to chase him.

The light faded. The day closed in. At the rate we were going we would soon need torches, which we had not brought. To cover more ground, we split up; Clemens took one side of the highway, Sentius the other. I went up ahead some distance, tethered my donkey to show where I started, then moved forward by myself on foot. Intent on searching as far as I could that day, I kept up a good pace. I glanced inside any tombs which had ready access; checked quickly around the back of all those I passed, whether open or locked; kept going steadily. Clemens and Sentius were supposed to pick up my mount in due course, then move on past me so we worked in relays.

They never caught me up. I covered the ground faster than they did. Informers learn to be meticulous without wasting time. This was no area to hang about. Just because the road and the tombs seemed deserted did not mean they really were. You need not believe in ghosts to be aware of an unseen presence. We were all being watched, undoubtedly. I was just waiting for the moment when we found out who it was and what they wanted.

At one chilly monument, a whimsical pyramid, a flight of tiled steps led down into a pitch-dark interior. I could not bring myself to step past the creaking door; irrational fear that it would slam shut behind me held me on the threshold. I had grown so nervous in that lonely place I shouted out, 'Is anybody in there?'

Nobody answered, but my call had been heard. As I turned on the steps, heading out of the tomb, I was suddenly accosted. With a wild but silent movement, someone – or something – all in white reared up above me on the mausoleum roof. This restless ghoul was hooded, jerking its wrists above its head as if jangling spectral bangles. I was so startled, my foot slipped on damp vegetation and I fell heavily. Then the figure continued its wild dance, letting out a high ghostly cry.

XXIV

The cavorting spectre slowed its roof top dance. 'Hoo! Hoo! Are you alive or dead?' 'I'm bloody well not happy!' I sat up awkwardly in agony. I had twisted my ankle as I slid on the tiled steps. 'Stop jiggling about.' 'Hoo-oo are you?' The faint, papery voice sounded like a bat squeak. 'Name's Falco. Who in Hades are you?' 'In Hades, out of Hades… Flitting bodiless and airy… the unburied dead.' Someone around here had read too much Virgil.

'Suit yourself.' I was in no mood for paranormal crackpots. When in pain, I tend towards the pedantic. 'Tell me, spirit, whose corpse do you represent?' 'I used to be called Zoilus.' I closed my eyes. I was a sensible man. I had an urgent job to do. The Furies must really be bearing a grudge today, if the spiteful ones – sorry, ladies, the kindly ones – had stuck me here, talking to a ghost. Wincing, I forced myself upright. I took a few hops to firm ground, where I tested my ankle. Somehow, the spirit of Zoilus had jumped down from the tomb; he bobbed up in front of me. He was still waiting for me to react in fright, and I still wasn't having it. Twilight had descended. By some trick he could have learned in a theatre, he seemed unearthly, wavering around me, his shifting white robes luminescent; only a pale orb that was almost without features lurked in his hood where his face should be. This ghost was light on his feet. In fact he did not seem to have any feet. He had mastered a smooth glide as if he floated several inches off the ground.

'Hoo! Hoo! Give me the fare for Charon!' So that was his game. I felt better for knowing. His squeaky tone was wheedling now, like any human beggar. 'Help me pay the ferryman, master.'

He had gone to more trouble with his story than most supplicants do, so I fetched out a coin and promised him the fee to cross the Styx if he would tell me whether he had seen a barbarian woman roaming friendless and solitary like him. He let out a shriek. I jumped. 'Death! Death! Bringer of death,' wailed the pallid sprite – rather pointlessly, if Zoilus was already deceased.

Could he know about the decapitation of Gratianus Scaeva? Had the murder at the Quadrumatus villa become the latest hot news among the shades in Hades? Had Scaeva's soul rushed there after his violent death, indignantly protesting? Were the bored spirits now flocking together to hear this news, all twittering with faded voices in Pluto's underworld forum – by Pluto, why was I messing about on a lonely road all day, when I could just ask this spook to help me out: get him to ask Scaeva's ghost, Hoo-oo did you in then?

I offered the coin. He did not take it. Whether unburied dead or simply restless, half-demented human, Zoilus darted away from me, rapidly executing that liquid glide backwards. Then he vanished. He must have jumped behind a tomb, yet it seemed as if he folded himself up and slipped into the very air, becoming bodiless and invisible. I called out. Nobody answered.

He had left me for a reason. As he slithered away into nothing, at last I encountered the runaway slaves. A scatter of them rose from the ground silently around me. I looked frantically for Clemens and Sentius, but they were nowhere. I was alone and unarmed, with dusk closing in. Zoilus had been more of an irritation than a threat; now that he was gone, I yearned for his crazy presence.

I had new companions, and I was even less happy. As the dark figures gathered in number, I remembered Petronius' sombre words of warning. If these beings could scare off a ghost, or a man who believed he was a ghost, I had reason to feel genuinely frightened.