'His heart?' I said.

'That's right. Look at these valves...' He turned his head to me, frowning. 'He died of something horses don't get.' He thought it over. 'It's a great pity we couldn't have had a blood sample before he died.'

'There's another horse at Henry Thrace's with the same thing,' I said. 'You can get your blood sample from him.'

He straightened up from bending over the heart, and stared at me.

'Sid,' he said. 'You'd better tell me what's up. And outside, don't you think, in some fresh air.'

We went out, and it was a great deal better. He stood listening, with blood all over his gloves and down the front of his overalls, while I wrestled with the horrors in the back of my mind and spoke with flat lack of emotion from the front.

'There are...or were...four of them,' I said. 'Four that I know of. They were all top star horses, favourites all winter for the Guineas and the Derby. That cla.s.s. The very top. They all came from the same stable. They all went out to race in Guineas week looking marvellous. They all started hot favourites, and they all totally flopped. They all suffered from a mild virus infection at about that time, but it didn't develop. They all were subsequently found to have heart murmurs.'

Ken frowned heavily. 'Go on.'

'There was Bethesda, who ran in the One Thousand Guineas two years ago. She went to stud, and she died of heart failure this spring, while she was foaling.'

Ken took a deep breath.

'There's this one,' I said, pointing. 'Gleaner. He was favourite for the Guineas last year. He then got a really bad heart, and also arthritis. The other horse at Henry Thrace's, Zingaloo, he went out fit to a race and afterwards could hardly stand from exhaustion.'

Ren nodded. 'And which is the fourth one?' I Iooked up at the sky. Blue and clear. I'm killing myself, I thought. I looked back at him and said, 'Tri-Nitro.'

'Sid!' He was shocked. 'Only ten days ago.'

'So what is it?' I said. 'What's the matter with them?'

'I'd have to do some tests, to be certain,' he said. 'But the symptoms you've described are typical, and those heart valves are unmistakable. That horse died from swine erysipelas, which is a disease you get only in pigs.' Ken said, 'We need to keep that heart for evidence.'

'Yes,' I said.

Dear G.o.d....

'Get one of those bags, will you?' he said. 'Hold it open.' He put the heart inside. 'We'd better go along to the Research Centre, later. I've been thinking.... I know I've got some reference papers there about erysipelas in horses. We could look them up, if you like.'

'Yes,' I said. He peeled off his blood-spattered overalls. 'Heat and exertion,' he said. 'That's what did for this fellow. A deadly combination, with a heart in that state. He might have lived for years, otherwise.'

Ironic, I thought bitterly.

He packed everything away, and we went back to Henry Thrace. A blood sample from Zingaloo? No problem, he said.

Ken took enough blood to float a battleship, it seemed to me, but what was a litre to a horse which had gallons. We accepted reviving Scotches from Henry with grat.i.tude, and afterwards took our trophies to the Equine Research Establishment along the Bury Road.

Ken's office was a small extension to a large laboratory, where he took the bag containing Gleaner's heart over to the sink and told me he was washing out the remaining blood.

'Now come and look,' he said. This time I could see exactly what he meant. Along all the edges of the valves there were small k.n.o.bbly growths, like baby cauliflowers, creamy white.

'That's vegetation,' he said. 'It prevents the valves from closing. Makes the heart as efficient as a leaking pump.'

'I can see it would.'

'I'll put this in the fridge, then we'll look through those veterinary journals for that paper.'

I sat on a hard chair in his utilitarian office while he searched for what he wanted. I looked at my fingers. Curled and uncurled them. This can't all be happening, I thought. It's only three days since I saw Trevor Deansgate at Chester. If you break your a.s.surance, I'll do what I said.'

Here it is,' Ken exclaimed, flattening a paper open. 'Shall I read you the relevant bits?'

I nodded.

'Swine erysipelas - in 1938 - occurred in a horse, with vegetative endocarditis- the chronic form of the illness in pigs.' He looked up. 'That's those cauliflower growths. Right?'

'Yes.'

He read again from the paper. 'During 1944 a mutant strain of erysipelas rhusiopathiae appeared suddenly in a laboratory specialising in antisera production and produced acute endocarditis in the serum horses.'

'Translate,' I said. He smiled. 'They used to use horses for producing vaccines. You inject the horse with pig disease, wait until it develops antibodies, draw off blood, and extract the serum. The serum, injected into healthy pigs, prevents them getting the disease. Same process as for all human vaccinations, smallpox and so on. Standard procedure.'

'O.K.,' I said. 'Go on.'

'What happened was that instead of growing antibodies as usual, the horses themselves got the disease.'

'How could that happen?'

'It doesn't say, here. You'd have to ask the pharmaceutical firm concerned, which I see is the Tierson vaccine lab along at Cambridge. They'd tell you, I should think, if you asked. I know someone there, if you want an introduction.'

'It's a long time ago,' I said. 'My dear fellow, germs don't die. They can live like time-bombs, waiting for some fool to take stupid liberties. Some of these labs keep virulent strains around for decades. You'd be surprised.'

He looked down again at the paper, and said, 'You'd better read these next paragraphs yourself. They look pretty straightforward.' He pushed the journal across to me, and I read the page where he pointed.

(1) 24-48 hours after intra-muscular injection of the pure culture, inflammation of one or more of the heart valves commences. At this time, apart from a slight rise in temperature and occasional palpitations, no other symptoms are seen unless the horse is subjected to severe exertion, when auricular fibrillation or interference with the blood supply to the lungs occurs; both occasion severe distress which only resolves after 2-3 hours rest.

(2) Between the second and the sixth day pyrexia (tempera- ture rise) increases and white cell count of the blood increases and the horse is listless and off food. This could easily be loosely diagnosed as 'the virus'. However examination by stethoscope reveals a progressively increasing heart murmur. After about ten days the temp- erature returns to normal and, unless subjected to more than walk or trot, the horse may appear to have recovered. The murmur is still present and it then becomes necessary to retire the horse from fast work since this induces respiratory distress.

(3) Over the next few months vegetations grow on the heart valves, and arthritis in some joints, particularly of the limbs, may or may not appear. The condition is perma- nent and progressive and death may occur suddenly following exertion or during very hot weather, some- times years after the original infection.

I looked up. 'That's it, exactly, isn't it,' I said.

'Bang on the nose.'

I said slowly, 'Intra-muscular injection of the pure culture could absolutely not have occurred accidentally.'

'Absolutely not,' he agreed.

I said, 'George Caspar had his yard sewn up so tight this year with alarm bells and guards and dogs that no one could have got within screaming distance of Tri-Nitro with a syringeful of live germs.'

He smiled, 'You wouldn't need a syringeful. Come into the lab, and I'll show you.'

I followed him, and we fetched up beside one of the cupboards with sliding doors that lined the whole of the wall. He opened the cupboard and pulled out a box, which proved to contain a large number of smallish plastic envelopes.