I did start to work along one block, scanning the crowds as I fought round the gangway which divided the first and second of the three tiers of seats. Staring up sideways soon made me dizzy, and the massed faces merged into one indistinguishable blur.

This was no way to find a bug in a sack of barley. I nipped down the next stairway back into the arcades, then passed among the booths and the knots of prostitutes, showing everyone the little plaque Larius had drawn for me. When I reached the business end of the stadium I found Famia, who introduced various other people to whom I also exhibited my sketch of Pertinax.

After that the only decent thing was to make a show of inspecting my brother-in-law's efforts to turn out my racehorse handsomely.

With his tail tied high and his ragged mane plaited, Little Sweetheart looked as good as he ever would, though still a disaster. Famia had found him a saddlecloth, though he would have to manage without the gold fringes and pearl-encrusted breastbands his rivals were tricked out in. To Famia's disgust, I insisted that even though he was bound to lose sensationally, if this was the only time in my life I could field my own racehorse, I would run the Sweetheart for the Blues; Famia made a stink, but I was adamant.

Ferox looked a million in his glossy mulberry coat; you could shave in his flanks. He was attracting plentiful attention as he and the Sweetheart waited side by side in the Cattle Market Forum; the buzz among the bookmakers was scintillating. Ferox would be running in the colours of the Marcellus-Pertinax faction, the Whites.

I acted up as an owner for a while, allowing the punters to jibe at me for the faith they assumed I placed in my gangling scruff, then Famia and I went off for lunch.

'You betting, Falco?'

'Just a flutter.'

Famia would think it bad form for an owner to back another horse, so I did not tell him Larius was putting fifty gold sesterces on Ferox for me: all my spare cash.

•

When we came back to the Circus they had started the horse races, though from our place on the card we had another hour to wait. I went to check that the Sweetheart was keeping Ferox calm, in order to safeguard my wager. While I was petting Ferox, I noticed a small, nervous, stuffed-vineleaf vendor hopping about: clearly a man with a gastric disturbance-or something significant to say. He said it to Famia, though they were looking at me. Money changed hands. The vineleaf tray skedaddled, then Famia came across.

'You owe me ten denarii.'

'See me tomorrow when I call in my bet!'

'Your man is in the second tier, on the Aventine side, near the judges' box; he's put himself level with the finishing line.'

'How can I get near him unobtrusively?' Famia cackled that with my well-known ugly visage it would be impossible. But he was useful: five minutes later I had slipped through one of the dark stalls at the starting gate end, and squeezed myself through the double doors.

Noise, heat, smells and colour assaulted me. I was in the arena, right down on the track. I had a bucket and a shovel. I waited until the riders passed, then wandered out across the sand, making a desultory scoop at the ground as I crossed the diagonal starting line. I reached the central barrier, the spina, feeling that I stood out like a pimple on a barrister's nose-but Famia was right: nobody ever notices the slaves who sweep up dung.

They were running one of those show pieces where bareback riders stand astride two horses at once-dramatic, though comparatively slow. The trick is to have the horses well trained, and to keep a good rhythm; my brother could do it. (My brother was the flashy, athletic type with a streak of blatant stupidity; he tried anything that risked his neck.)

Standing up against the marble podium, the huge size of the Circus was breathtaking. The width across was half the length of a normal stadium, and from the white chalk of the starting line the far end seemed so distant I had to squint. Immediately above me as I ambled up the length of the spina, towered magnificent shrines and statues; Apollo, Cybele, Victory. For the first time I appreciated the workmanship on the great gilded bronze screen which stood between the senatorial seats and the arena itself. Beyond them yawned two tiers of marble terracing and a third tier of wood, then the closed-in upper gallery with standing room only. As I made a random pass with my bucket, I noticed how the sand had a glistening mica rim near the podium and the spina, where coloured chippings from past gaudy occasions had worked to the edges of the track. They never have awnings at the Circus; you could frizzle up an omelette on the sand. Everywhere had a constant odour of warm horseflesh above the lunchtime garlic and ladies' cologne.

The spina was ornamented with mosaics and gilt, against which I must have appeared a small, dark dot, like some tiresome, meandering bug. In the space of two races I shuffled up as far as the huge red granite Egyptian obelisk which Augustus had set in the very centre of the spina; then I edged on nearer to the finishing line and the judges' box. This was where the seats were always most warmly packed. At first the mass of faces melded into one great fudge of humanity, but as my confidence grew I began to see details: women shuffling their footstools and hoisting their stoles over one shoulder, men red-faced and bilious in the sun after lunch, soldiers in uniform, children squirming restlessly or fighting in the aisles.

There was a break between races, filled with tumblers and acrobats. Spectators moved about. I squatted against the podium, dry-eyed in the dust, while I began a methodical survey of the second tier. It took me twenty minutes to find him. As I did I thought he spotted me too, though he looked away. Once I pinpointed him, it seemed impossible that I could have missed his bad-tempered physiognomy before.

I sat still and went on searching. Sure enough, two rows lower down and ten places along I found Anacrites himself. Some of the time he was watching Pertinax, but mostly he stared round at the other seats. I knew who he was looking for! At the far end of the row where Pertinax was sitting and again higher up were two spies I recognized who formed a triangle with Anacrites, penning in the man I wanted and keeping him safe from me. None of them looked at the arena while I was crouching there.

I stood up. So did Pertinax. I started to cross the track towards the gilded screen. He moved along the row of seats. He had seen me. I knew it, and so did Anacrites, though he could not work out where I was. Stumbling over other people's feet, Pertinax reached a gangway. Even if I climbed over the screen, in among the indignant nobility on their marble thrones, he would be off down the stairs and out of the nearest vomitarium long before I got near. Meanwhile Anacrites suddenly shouted to one of the aediles' heavy squad and gestured unmistakably at me. I was not only losing Pertinax, but about to be arrested myself.

Then another shout aroused me, amid pounding hooves. I looked up into the huge grinning teeth of a beribboned black stallion bearing straight down on me. Trick saddle-men: this time two men in barbarian trousers, linking arms as they stood upright on a single horse. With a fiendish cry and a wild flash of eyeball one leaned out sideways as the other balanced him. They scooped me up like a disreputable trophy. We shed the second rider then careered on, with me as terrified ballast waving my dung shovel and trying to look as if this mad ride was the best fun I had ever had.

The crowd loved us. Anacrites hated it. Not being a fool who fancied himself as a horseman, so did I.

We swept right round the three conical goal posts and the altar of Consus at the end of the spina, slewing at a nerve-racking angle as we turned. Then we sped back along the whole length of the stadium on the far side. In a screech of polished hooves I was dropped at the starting gates. Famia dragged me in.