This was a Ministry of Defence thing and they'd got something so big on the board that they'd panicked and thrown us a crash-access and the Bureau hadn't been able to stop them. Control had been kicked into motion with almost nothing to go on: we had to reach Tewson as fast as we could and we didn't have to ask any questions. There was obviously a chance that he'd show up again at the Golden Sands but they couldn't give us time to mount an orderly snatch and that was all right but they couldn't have it both ways: they'd hair-triggered Mandarin to the point where the target was so sensitive that I'd almost certainly blow it before I could get there.

Tewson was the target: Tewson and the rig. And the instant they realized we were getting too close they'd whip him into China. Tell you what London had sent me here to do: I had to stalk a bird bare-handed and catch it before it flew up.

Bloody London for you.

The cord tautened again and I was pulled sideways, getting fed up with it. When I broke surface with the faceplate I saw the configuration had altered, but not too much: I was learning how to do it better, every time. The flare at the tip of the stack made a diffused glow and I took off the mask and demisted it, pulling the mouthpiece away for a moment to drag in the dry taste of ozone.

The rig looked about half a mile away and as far as I could see there was no movement on board: the lights were stable and their pattern didn't change. I'd have liked to audio-survey for a few seconds but it wouldn't be easy: it wouldn't be any good just pushing one ear through the surface because it'd be full of water: I'd have to drain it and that meant putting the whole of my head through and if they had any short-range scanners they'd pick up the blob.

I went down again and listened below water, holding my breath for five seconds. Nothing.

From the information Ferris had picked up from local sources the oil rig had been operational for three months: the crude was said to be already on stream and they'd set up a tanker shuttle between the rig and the refineries along the South China coast. If they were burning residual lean gas at the flare pilot they must be running at production capacity and they ought to be working round the clock because on an operational oil rig there's no difference between night and day.

There was on this one. No sound of machinery. No sound of life.

I checked the time at 01.46. Airstream normal, buoyancy easy to manage, the spare tanks no real problem. During the next long haul I made two brief visual checks from the surface and then stayed below: the faint yellow stain of the flare pilot was now on the surface and I used it as my lode star until the dark trellis pattern of the substructure began showing against the sea bed a hundred feet below.

The glow of the derrick bases flared softly for two or three minutes on the surface and then dimmed out as I arched my back slightly and brought my head down, diving to twenty feet on the gauge. I was assuming there were look-outs and the air tanks on my back could pick up scattered light. It was almost totally dark at this depth and I stopped kicking and drifted, using my free hand to bring me more or less upright. My eyes had been used to the moonglow for some time now, and the flare pilot and then the white reflected light from the derricks had closed the irises to something like half their original diameter, and I needed time to accommodate. The trellis pattern of the rig was very faint now, although I was closer, and the sea was a dark wall around me.

Silence.

Then the long-drawn sound of my inhalation, hollow and strange, as if I could hear only the echo, and not the sound itself. Silence again and then the bubbling as my breath rose from behind me and floated above my head. At each interval between inhalation and exhalation the silence was total.

Slight stress beginning because of this, and because of the dim light. The onset of disorientation: normal but uncomfortable. The organism was starting to ask where it was, what it was doing here where it couldn't see things very well, couldn't hear things. To be ignored, or better still contained. Keep still and keep quiet, listen to what you can: the sound of your own life-giving breath. Look at what you can: the faint pattern of the girders, and above them the square configuration of the superstructure, delineated by the night glow of the sky, and the diaphanous cloud of debris drifting past as the current flowed from the south.

Breathe. See. Hear. All is normal. Relax.

The nylon cord tugged slightly as the current moved the reserve tanks, turning me gently round. With one hand I spun myself slowly back, to keep the girders in sight. They were becoming clearer, darker against the sands beyond, except where the cloud floated, moving nearer against my faceplate, and lower. Its edge was blotting out part of the girders, as if it were opaque, and becoming larger. One of the background girders ran straight upwards from it, thin and perpendicular, and I looked down to follow it, then up again to watch the cloud itself. Its configuration had altered suddenly, and protrusions appeared, perfectly equidistant; and as it bumped against me I put my free hand out to push it away, but it wasn't easy because it was a cable above it, not a girder in the background, and these protrusions bumping against me in the current were detonation horns.

The shock was explosive because the nerves were being hit by imagination as well as fact and in an effort to keep me alive the imagination was picturing for me what would happen if I touched that thing again and for an instant I saw the blinding light and felt the tearing apart of life in the roaring waters and then the inrush of eternal dark.

Christ sake stick to the facts and think, try to think, get back to where you were a second ago, the bloody thing hasn't gone off and you're still alive so do something to stay that way. It could have blown us right — shuddup you snivelling little tick — you'll never see Moira again if it — get out of my head, it didn't go off and we're just the same as we were before but we have to think.

There wouldn't just be this one.

It drifted away a little on the current and then came back, tethered by the thin steel cable. I moved away slowly, fanning the water with both hands, retreating from it but not too far.

They wouldn't have put just this one here. There wouldn't be any point. I was in a minefield.

Fanning with my hands, keeping upright, maintaining the organism in the vertical attitude it was used to, so that it could operate without too much stress. But more data was being rammed into the brain. A whole mass of it to do with my hands, information about my hands, information and questions, why were they both free, my hands, where had the -

I don't know.

Turn. Spin slowly and mind the air tanks because if they hit that — take care, take normal care, if it was a beach ball the tanks would never hit it, it's only because it's full of TNT that you think they might, relax. Turn slowly and look, look everywhere. It can't have drifted far.

Instinct is devoted almost totally to keeping us alive and it functions at nerve speed and it doesn't even refer to higher authority: it doesn't waste time asking the brain what to do. It acts. It short-circuits the normal system that processes the data and presents it for decision-making and signals the motor nerves and contracts the muscles. It doesn't demand cerebration because that would slow the action. And it can't think for itself: it thinks as much as a gun thinks after the trigger's been pulled. If it sees a spark coming it shuts your eyes and if it sees a snake it stops you dead in your tracks and if it sees a high-explosive mine it frees your hands and drives them flat against the water to push you away and that was why I'd lost my hold on the nylon cord and that was why the reserve tanks and the radio and the rations were drifting somewhere in the gloom where I couldn't see them.