'I'll go in my car.'

'Sure,' said the man. He pulled the knitted hat down round his ears. 'I'll ask Mr Cruyer to call you and confirm, shall I?' He was careful not to grin but my caution obviously amused him.

'Do that,' I said. 'You can't be too careful.'

'Will do,' he said, and gave me a perfunctory salute before opening the car door. 'Anything else?'

'Nothing else,' I said. I didn't let go of the gun until they'd driven away. Then I went indoors and poured myself a malt whisky while waiting for Cruyer's call. Fiona arrived before the phone rang. She gave me a tight embrace and a kiss from her ice-cold lips.

Cruyer was not explicit about anything except the address and the fact that he'd been trying to get me for nearly an hour, and would I please hurry, hurry, hurry. Not wanting to arrive there complete with folding bed, I lifted it from the roof rack before leaving. The exertion made me short of breath and my hands tremble. Or was that due to the confrontation with the man from the car? I could not be sure.

The part of south London that takes its name from the Surrey County cricket ground is not the smart residential district that some tourists might expect. The Oval is a seedy collection of small factories, workers' apartments and a park that is not recommended for a stroll after dark. And yet, tucked away behind the main thoroughfares, with their diesel fumes, stray cats and litter, there are enclaves of renovated houses – mostly of Victorian design – occupied by politicians and civil servants who have discovered how conveniently close to Westminster this unfashionable district is. It was in such a house that Cruyer was waiting for me.

Dicky was lounging in the front room reading The Economist. He habitually carried such reading matter rolled up in the side pocket of his reefer jacket which was now beside him on the sofa. He was wearing jeans, jogging shoes and a white roll-neck sweater in the sort of heavyweight wool that trawler-men require for deck duty in bad weather.

'I'm sorry you couldn't reach me,' I said.

'It doesn't-matter,' said Dicky in a tone that meant it did. ' Trent has taken an overdose.'

'What did he take? How bad is he?' I asked.

'His sister found him, thank God,' said Dicky. 'She brought him here. This is her house. Then she called a doctor.' Dicky said doctor as another man might say pervert or terrorist. 'Not one of our people,' Dicky went on, 'some bloody quack from the local medical centre.'

'How bad is he?'

Trent? He'll survive. But it's probably a sign that his Russian pals are turning the screws a bit. I don't want them tightening the screws to the point where Trent decides they can hurt him more than we can.'

'Did he say that? Did he say he's coming under pressure?'

'I think we should assume that he is,' said Dicky. 'That's why someone will have to tell him the facts of life.'

'For instance?'

'Someone is going to have to explain that we can't afford to have him sitting in Moscow answering the questions that a KGB debriefing panel will ask. Losing a few secret papers is one thing. Helping them build a complete diagram of our chain of command and the headquarters structure, and filling in personal details about senior officers for their files would be intolerable.' Dicky held the rolled-up magazine and slapped the open palm of his left hand with it. Ominously he added, 'And Trent had better understand that he knows too much to go for trial at the Old Bailey.'

'And you want me to explain all that?' I said.

'I thought you'd already explained it to him,' said Dicky.

'Did it occur to you that a suicide attempt might indicate that he's already been pressed too hard?'

Dicky became absorbed in the problem of rolling The Economist up so tightly that no light could be seen through it. After a long silence he said, 'I didn't tell the stupid bastard to sell out his country. You think because he's a Balliol man I want to go easy on him.' He got out his cigarettes and put one in his mouth unlit.

'I never went to college,' I said. 'I don't know what you're talking about.'

He heaved himself off the sofa and went to the mantelshelf where he rummaged for matches and pulled at a flower petal to see if the daffodils were plastic; they weren't. 'You didn't go to college but sometimes you hit the nail on the head, Bernard old friend. I've been thinking of that conversation you had with Bret Rensselaer this afternoon. It was only sitting here tonight that I began to see what you were getting at.' I'd never seen Dicky so restless. He found a matchbox on the shelf, but it was empty.

'Is that so?'

'You think everything's coming up too neat and tidy, don't you? You don't like the way in which that material implicating Trent has conveniently come into Frank's hands in Berlin. You're suspicious about his being on duty the night that damned radio intercept was filed. In short, you don't like the way everything points to Giles Trent.'

'I don't like it,' I admitted. 'When I get all my questions answered fully, I know I'm asking the wrong questions.'

'Let's cut out all this nebulous talk,' he said. He put the matchbox back on the shelf, having decided not to smoke. 'Do you think Moscow know we are on to Trent? Do you think Moscow intend to use him as a scapegoat?' Carefully he put his unlit cigarette back into the packet.

'It would be a good idea for them,' I said.

'To make us think every leak we've suffered for the last few years has been the work of Trent?'

'Yes, they could wipe the slate clean like that. We put Trent behind bars and heave a sigh of relief and convince ourselves that everything is fine and dandy.'

Now Dicky used the magazine to imprint red circles on his hand, examining the result with the sort of close scrutiny fortune tellers give the palms of wealthy clients.

'There would be only one reason for doing that,' said Dicky. He looked up from his hand and stared into my blank face. 'They'd have to have someone placed as well as Trent… someone who could continue to provide them with the sort of stuff they've been getting from Trent.'

'Better,' I said. 'Much better.'

'Why better?'

'Because Moscow Centre always like to get their people home. They'll spend money, arrest some poor tourist to use as hostage, or even spring from jail an agent serving a sentence to swop him. But they really try hard to get their people home.'

'I could tell you a few people who now find they don't like it "at home",' said Dicky.

'That doesn't make any difference,' I said. 'The motive that Moscow Centre play upon is getting them safely back to Russia… medals and citations and all that hero bullshit that Moscow do so well.'

'And there is no sign yet that they are going to try getting Trent back to Moscow.'

'And that will spoil their record,' I said. 'They'd have to have a really good reason for letting Trent fall off the tightrope. There's only one sort of motive they could have, and that's positioning or making more secure another agent. A better agent.'

'But maybe the Russians don't know we're on to him.'

'And maybe Trent doesn't want to go to Moscow. Yes, I thought of both those possibilities, and either could be true. But I think Trent is going to be deliberately sacrificed. And that would be very unusual.'

'This other person,' said Dicky. 'This other agent that Moscow might already have in position… You're talking about someone at the very top? Am I right?'

'Look at the record, Dicky. We haven't run a good double agent in years and we haven't landed any of their important agents either. That adds up to one thing only: someone here is blowing everything we do,' I said. 'We've had a long string of miserable failures, and some of them were projects that Trent had no access to.'

The record can be a can of worms – we both know that,' said Dicky. 'If they had someone highly placed, they wouldn't be stupid enough to act on everything he told them. That would leave a trail a mile wide. They are too smart for that.'