We again went to the sales: I seemed to have spent half a lifetime round that sale ring, and Luke now owned twenty-eight yearlings he had not yet seen. I had signed cheques on his behalf for nearly two million pounds and was tending to dream about it at night. There was only the Saturday morning left now, an undistinguished programme according to the catalogue, the winding-down after the long excitements of the week. I went early by habit and with only short premeditation bought very cheaply the first lot of the day, an undistinguished-looking liver chestnut colt whose blood lines were sounder to the inspection than his spindly legs. One couldn't have foretold on that misty autumn morning that this was the prince who would sire a dynasty, but that in the end was what happened. My mind, as I signed for him and arranged for him to be sent along the road to Mort's stable, was more immediately on the conversation I'd had with Jonathan on the telephone the evening before.

'I want to talk to Angelo's father,' I said. 'Do you remember where he lived?'

'Of course I do. Welwyn Garden City. If you give me a minute, I'll find the street and the number.' There was a pause while he searched.

'Here we are. Seventeen, Pemberton Close. He may have moved, of course, and don't forget, William, he won't be in the least pleasant. I heard he was threatening all sorts of dire revenges against me after Angelo was convicted, but I didn't hang around long enough for him to get going.'

'Angelo seems to depend on him for cash,' I said.

'That figures.'

'Angelo's making a right balls-up of the betting system. He's losing his father's money and he's blaming me for it, and stoking up again towards volcanic eruption with me as the designated target for the lava flow.'

'He's an absolute pest.'

'He sure is. How does one rid oneself of a monster that won't go away? Don't answer that. Engineering Angelo back into jail permanently is all I can think of, and even then I would need to do it so that he didn't know who'd done it, and would it even on the whole be fair?'

'Provocation? Put a crime in his way and invite him to commit it?'

'As you say.'

'No, it wouldn't exactly be fair.'

'I was afraid you wouldn't think so,' I said.

'Nothing much short of murder would put him back inside for the whole of his life. Anything less and he'd be out breathing fire again, as you said before. And however could you line up a living victim?'

'Mm,' I said, 'it's impossible. I still think the only lasting solution is to make Angelo prosper, so I'll see if I can persuade his old dad to that effect.'

'His old dad is an old rattlesnake, don't forget.'

'His old dad is in a wheelchair.'

'Is he?' Jonathan seemed surprised. 'All the same, remember that rattlesnakes don't have legs.'

I reckoned that on that Saturday afternoon Angelo would still be blundering around the bookies on Newbury racecourse and that his father might have stayed at home, so it was then that I drove to Welwyn Garden City, leaving Cassie wandering around the cottage with a duster and an unaccustomedly domestic expression.

The house at number seventeen Pemberton Close proved to be inhabited not by Harry Gilbert but by a stockbroker, his chatty wife and four noisy children on roller skates, all of them out in the garden.

'Harry Gilbert?' said the wife, holding a basket of dead roses. 'He couldn't manage the stairs with his illness. He built himself a bungalow full of ramps.'

'Do you know where?'

'Oh sure. On the golf course. He used to play, poor man. Now he sits at a window and watches the foursomes go by on the fourteenth green. We often wave to him, when we're playing.'

'Does he have arthritis?' I asked.

'Good Lord, no.' She made a grimace of sympathy. 'Multiple sclerosis. He's had it for years. We've seen him slowly get worse… We used to live four doors away, but we always liked this house. When he put it up for sale, we bought it.'

'Could you tell me how to find him?'

'Sure.' She gave me brisk and clear instructions. 'You do know, don't you, not to talk about his son?'

'Son?' I said vaguely.

'His only son is in prison for murder. So sad for the poor man. Don't talk about it, it distresses him.'

'Thanks for warning me,' I said.

She nodded and smiled from a kind and unperceiving heart and went back to tidying her pretty garden. Surely goodness and mercy all thy days shall follow thee, I thought frivolously, and no monsters who won't go away shall gobble thee up. I left the virtuous and went in search of the sinner, and found him, as she'd said, sitting in his wheelchair by a big bay window, watching the earnest putters out on the green.

The wide double front doors of the large and still new-looking one-storey building were opened to me by a man so like Angelo at first sight that I thought for a fearsome moment that he hadn't after all gone to the races; but it was only the general shape and colouring that was the same, the olive skin, greying hair, unfriendly dark eyes, tendency to an all-over padding of fat.

'Eddy,' a voice called. 'Who is it? Come in here,'

The voice was as deep and harsh as Angelo's, the words themselves slightly slurred. I walked across the polished wood of the entrance hall and then across the lush drawing room with its panoramic view, and not until I was six feet away from Harry Gilbert did I stop and say I was William Derry.

Vibrations could almost be felt. Eddy, behind me, audibly hissed from the air leaving his lungs. The much older version of Angelo's face which looked up from the wheelchair went stiff with strong but unreadable emotions, guessed at as anger and indignation, but possibly not. He had thinning grey hair, a grey moustache, a big body in a formal grey suit with a waistcoat. Only in the lax hands was the illness visible, and only then when he moved them; and from his polished shoes to the neat parting across his scalp it seemed to me that he was denying his weaknesses, presenting an outwardly un-crumbled facade so as to announce to the world that authority still lived within.

'You're not welcome in my house,' he said.

'If your son would stop threatening me, I wouldn't be here.'

'He says you have tricked us like your brother.'

'No.'

'The betting system doesn't work.'

'It worked for Liam O'Rorke,' I said. 'Liam O'Rorke was quiet, clever, careful and a statistician. Is Angelo any of those things?'

He gave me a cold stare. 'A system should work for everyone alike.'

'A horse doesn't run alike for every jockey,' I said.

'There's no similarity.'

'Engines run sweetly for some drivers and break down for others. Heavy-handedness is always destructive. Angelo is trampling all over that system. No wonder it isn't producing results.'

The system is wrong,' he said stubbornly.

'It may,' I said slowly, 'be slightly out of date.' Yet for Ted Pitts it was purring along still: but then Ted Pitts too was quiet, clever; a statistician.

It seemed that I had made the first impression upon Harry Gilbert. He said with a faint note of doubt, 'It should not have changed with the years. Why should it?'

'I don't know. Why shouldn't it? There may be a few factors that Liam O'Rorke couldn't take into account because in his time they didn't exist.'

A depressed sort of grimness settled over him.

I said, 'And if Angelo has been hurrying through the programs, skipping some of the questions or answering them inaccurately, the scores will come out wrong. He's had some of the answers right. You won a lot at York, so I'm told. And you'd have won more on the St Leger if Angelo hadn't scared the bookmakers with his boastfulness.'

'I don't understand you.' The slur in his speech, the faint distortion of all his words was, I realised, the effect of his illness. Articulation might be damaged but the chill awareness in his eyes said quite clearly that his intelligence wasn't.