For a moment I thought I saw a face; then it was gone.

Chandler, standing beside me, hadn't spoken a word for ten minutes. No one had.

The smell of the river came on the night air, bland and rotten. We went on watching, and I glimpsed a black wet fin disturbing the surface not far from the bank. Bubbles popped in the soft light of the lamps, tracing a regular pattern.

The face came again and I kept my eyes on it, but it must have been a patch of rubbish or something, surfacing on the slow current; it vanished again. From across the river Big Ben started chiming the prelude to the hour. The air was sultry after the heat of the long summer day.

On our left the small boat was moving downstream, the two men in it paying out the lines to the net. Someone on the bank swivelled the end floodlight, and we saw an oily black ripple as one of the divers neared the surface and rolled over, going down again. The eleventh chime of the clock faded to silence.

More people were walking down from the bridge, where they'd left their cars. The police had a barrier halfway along Riverside Walk, to keep them back. The inspector in charge of the operation was standing somewhere on the other side of Chandler, not speaking, leaving it to his team to get on with the job: they obviously knew what they were doing. -

I'd never met Chandler before; he was one of the new people, a pale thin man who kept his distance, afraid of questions until he felt sure of his ground. I'd only asked him a couple of things and he'd stared at me for a long time, as if I were a bloody fool; it was just that he didn't know the answers. None of them knew for certain who it was in the river here.

Tilson had said it was Sinclair, when I'd talked to him on the bridge earlier tonight.

The submersible lamps were swinging again, below water; the divers moved like shadows across the diffused light, nearer the surface now. The men in the boat had started calling to the land crew along the bank.

I hoped to God it wasn't Sinclair. He was one of the best we had.

Higher along the embankment, at the end of the bridge, the police were still taking flash photos of the wrecked car. From the little Tilson had told me, Sinclair — or whoever it was — had been thrown from the car into the river when it had crashed, or had been dragged out of the wreck and dropped off the bridge.

The light was getting brighter now, and soon one of the divers rose like a shark, his black finned body breaking the surface not far downstream; then another came into view and a lamp swung clear of the water and flashed across our eyes before a man on the bank grabbed it and steadied it. We were all leaning forward now, and I heard someone say: "Right. They've got him."

Chandler moved at last, poking his thin face towards the river, where two more divers were surfacing, pulling at the drag lines as the land crew took up the slack; then we saw the body as it floated clear of the long net, rolling in the turbulence with its white face showing and then darkening, showing again in the glare of the floods. They hauled him out and lowered him to the walkway, turning him onto his back and gently pulling his legs together. Chandler stooped over him.

An hour ago I'd been with a girl in the Gaslight Club, halfway through a late dinner and getting to know her, one of the Foreign Office staff, the only ones we were allowed to meet when we were on standby, for security reasons. A plain-clothes man from the Yard had come in and told me I was wanted, and I didn't argue because he'd mentioned the name Tilson.

I'd driven straight to the Thames with a police escort and found Tilson standing near the wrecked TR-4.

"Sinclair was coming in from Taiwan," he said plaintively, "with something to tell us, according to his signal from Calcutta. There was some trouble with the plane, and he had to switch flights." He gazed unhappily through his horn-rimmed glasses at the diving crew along the river.

"When did he get in?"

"About an hour ago. We'd cleared Customs for him."

Some people from the Yard were taking measurements of the TR-4's position, and bringing flash equipment. We moved away a bit to give them room.

"What was he doing here, for God's sake?" I asked Tilson. I was getting worried. They don't often go for us on our home ground, any more than we go for them at the embassies. Sinclair would have driven straight from the airport to our place in Whitehall if he'd had something so important to say that he couldn't put it in a signal.

"We think he was got at," said Tilson.

"Pretty obvious. He knew how to drive, for Christ's sake." A flashlight popped, freezing the scene, and I noticed some blood on the seat of the crashed car. "Who met him at the airport?" I asked Tilson.

"He landed thirty minutes early. They missed him."

I went cold suddenly. Tilson was keeping an awful lot back, I knew that now, but this was quite bad enough. Someone had let this man fly into London with some vital information in his head and they'd left him without an escort and now he was down there somewhere among the dead cats and the weeds with his mouth shut forever.

Tilson shuffled his feet, and I noticed he'd come here in such a hurry that he was still wearing the plaid slippers he used at the office. "I suppose what happened," he said miserably, "is that he picked them up in his mirror on his way to our place and led them clear just in time. Led them as far as here." Glass crackled under the men's feet as they moved around the car with their cameras.

"Did anyone see him crash?"

"Oh yes, several people. They said another car ran smack into him and drove off without stopping. But someone said he thought he saw the car stop, and two men go over to the wreck and pull the driver out. You know what witnesses are. We're doing what we can to spread the story of a drunk hit-and-run driver."

That was routine: this looked like a wet affair and the Bureau would try for an immediate blackout. The Bureau doesn't officially exist, and if anything awkward happens in public we go to ground. The police here wouldn't ask us any questions, because of our cards.

Tilson moved his feet again. "Sorry we had to break up your evening, old fruit. The thing is, we need to know for certain whether it's Sinclair, and you knew him better than most."

I'd left him keeping guard on the wreck, and come down here on foot along the embankment to report to Chandler, and now I looked into the dull blue stare of the man on the ground and said, "Yes, this is Sinclair."

People were still strolling along the Embankment fifteen minutes later as I drove beside the river, heading for Cheyne Gardens.

I'd thought of ringing the girl at her place and trying to patch up the evening, but it wouldn't have been much use, even if she agreed. Tonight I was grieving, and scared. I'd known Sinclair for a long time, and done some work with him in various parts of the world, tricky work that had taken him right to the edge of things, as it takes all of us when we're out there in the field; but they'd come for him and got him right on his home ground, and that hadn't happened before to any of us. In London they know where we are and we know where they are — mostly at the embassies — and there's no point in starting trouble because it could escalate and end in a massacre and shake the whole of the diplomatic structure.

But they'd gone for Sinclair with a purpose and nailed him down, and the thing that scared me was the knowledge that there must be something awfully big going on in the background, and going wrong.

And grief, yes, mixed in with the fright. We're meant not to care what happens to anyone else and we try to play it like that, because there's a high mortality rate among the field executives and any kind of friendship would bring the whole thing too close to us and we'd start breaking up. But we can't avoid contact when there's a big mission going and the heat comes on and the thing starts running wild: Sinclair had been in the helicopter when they'd pulled me out of that awful mess in Mecklenburg after I'd gone in too close and no one could find me — no one except Sinclair, who'd been turning the signals base inside out till he'd traced my last call and told them where I was: halfway across a minefield in the dark and with no support; my own bloody fault because I'd refused it, didn't want anyone getting in my way. The border guards had started firing and we put the chopper down three miles away on one skid and a rotor tip, wrecking the whole thing but getting out alive and with nothing to show for it except that Sinclair had started limping with his left -