The glow of the bug was moving across the chart between Lamma and Cheng Chau Islands. 'We're heading north of this one, Hei Chou, and turning approximately south-east, instead of rounding this group here. The long way round, but safer. As you see, all these islands are Chinese territory and most of them maintain garrisons and of course coastguard units.' He glanced up at the chronometer. 'I estimate we'll reach our position in half an hour. Let us say 01.15.'

We went back into the wardroom to keep out of their way.

'Everything going nicely,' Ferris said, but he didn't look at me. He was behaving rather well: every time one of the bulk head doors was slammed somewhere in the ship he gave a quick blink but that was all.

'Piece of cake,' I said, and began sorting out my gear. I didn't know what the conditions were out there: in an air drop you can study the target zone on your way down and pick out any features that could be dangerous or difficult, but all I knew on this trip was that the sea was calm, the temperature was in the region of 82 and moonrise had taken place twelve minutes ago. It wasn't much to know.

In ten minutes the ship began heeling slightly as we turned south-east and headed straight for the rig, fourteen or fifteen miles distant.

At 01.00 I went back to the control room, leaving Ferris looking at a copy of Penthouse, not really his cup of tea. His face had lost all its colour now and had a sheen of sweat on it. I noticed he'd pushed back the tuft of hair that had been sticking out.

They'd changed the chart on the dead-reckoning tracer and we were now on 341 with the glow of the bug moving midway between Yai Chou Island and the San-Men group. Our heading was 142 and the oil rig was four sea miles distant, dead on our course.

It was quieter now in the control room and I looked up at the blower grilles.

'We've shut some of them down,' said Ackroyd.

The engine-room telegraph was at half ahead both: we must have been slowing. Nobody was slamming doors any more. I looked at Ackroyd.

'Same ETA?'

'That's right.' His small bright eyes were very steady now as he watched the console.

01.04.

I went back to the wardroom. Ferris had pushed the copy of Penthouse to the end of the table and was sitting motionless, looking slightly upwards. I suppose that was where he was expecting to hear the crump, but the bloody things could go off anywhere, dead on our beam or below us, anywhere. He turned his head.

'Are we still on our ETA?'

'Yes.'

Time to suit up, isn't it?'

'Yes.'

Talc floated up under the lights as I got into the wet-suit and zipped it to the throat and started on the final checks: tank pressure, valves, harness, backpack, buckles, a quick exhalation through the mouthpiece to clear the check valves. All normal.

'Have you seen the rig yet?' Ferris asked me.

'Not yet. But it's there.'

I hit the valves a fraction to blow out any dust, making him flinch.

'Sorry.'

'Don't mind me.' I aligned the regulators, turning the butterfly bolts finger-tight.

'Are we slowing?' he asked.

I stopped work and listened.

'Yes.'

There wasn't anything more I could do before it was time to put on the scuba so I went into the control room. Ackroyd turned his head fractionally.

'We're rigged for silent running,' he said.

'Understood.'

We spoke very quietly. All sound background had gone: the engines were running at slow and they'd shut down all fans, blowers, pumps and auxiliary motors. Next to me I could hear the diving officer breathing.

'Want to take a look?'

I went to the periscope.

The oil rig was dead in sights, a black skeleton structure rearing from the moon lit surface of the sea. Longitude 114 , Latitude 22 . The target for Mandarin.

Chapter Twelve.

SOLO.

It was a quick piping note: the call of the sea swallow.

Ferris left the tape running while he helped me with the scuba.

'This side okay?'

'Another notch on the buckle.'

The weight of the tanks shifted.

A seaman came to the doorway.

'The captain wants you to know they've got radar.'

'On the rig?'

'Yes, sir.'

The bloody harness still wasn't right.

'Back another notch on both, will you?'

'Will do. There's no hurry.'

But I could hear his breathing. We'd passed through Chinese territorial waters between the islands and the last report from the control room was that we were now standing off the rig at one mile.

'Feel better?'