'I like a cheerful man,' I said acidly.

Mokhtar had disappeared about his private business but suddenly he appeared on top of a boulder about two hundred yards away. He gave a shrill whistle which attracted our attention, and waved both his arms. 'He's found something,' said Byrne, scrambling to his feet We went over to Mokhtar and that took us more than ten minutes in that ankle-breaking terrain. When we were fifty yards away Mokhtar shouted something, and Byrne said, 'He's found a truck. Let's see if it's a Land-Rover.'

As we scrambled on top of the boulder, which was as big as a moderate-sized stately home, Mokhtar pointed downwards, behind him. We walked over and stared to where his finger was pointing. There was a vehicle down there behind the boulder, and it was a Land-Rover. Or, at least, it had been – it was totally burnt-out. There was no sign of Billson or anyone else, and I suddenly realized that 1 wouldn't know Billson if I saw him. I was a damn fool for not having a photograph.

Byrne said, 'The black smoke would come from the burning tyres. Let's get down there.'

Going down meant going back the way we had come and walking around the boulder. As we came in sight of the Land-Rover, Byrne, in the lead, spread his arms to stop us. He spoke rapidly to Mokhtar who went on ahead, peering at the ground. Presently he waved and Byrne walked over to him, and they had a brief discussion before Byrne beckoned to me.

'There's been another truck here; its tracks are on top of those of the Land-Rover, and it went that way.' He pointed back in the general direction of the Toyota.

'Where's Billson?' My mouth was dry.

Byrne jerked his head at the Land-Rover. 'Probably in there – what's left of him. Let's see.'

He stood up and we walked over to -the Land-Rover. It was a total wreck – a burnt-out carcass; it sat on the ground, the wheel rims entangled in the steel reinforcing wires of what had been tyres. There was still a lingering stench of burning rubber in the air.

The window glass had cracked and some of it had melted, and the windscreen was totally opaque so that it was difficult to see inside. Byrne reached out and tugged at the handle of the door on the driver's side and cursed as it came away in his hand. He walked around and tried the other door. He jerked it open and looked inside, with me looking over his shoulder.

The inside was a mess. The upholstery had burned, releasing blackened coil springs, and even the plastic coating of the driving wheel had burnt away, leaving bare metal. But there was no body, either in front or on the rear seats.

We went around to the back and got the tailgate open, to find scant remnants of what appeared to be two suitcases. Again, no body. I said, 'The other truck must have taken him away.'

'Maybe,' said Byrne noncommittally. He poked around a bit more in the ruined Land-Rover, then he straightened up. 'Did Paul Billson have any enemies?'

'He may have had.' I went cold as I realized we were speaking of Billson in the past tense just as his half-sister had done. I said, 'I hardly think he'd have the kind of enemy who would follow him to the middle of the Sahara to kill him.'

'Mmm.' Byrne made a nondescript noise and continued his examination. 'I've seen lots of burnt-out trucks,' he said. He picked up a jerrican lying to one side, snapped open the cap, and sniffed. 'He had gas in her e. He must have been carrying it in the back there, because he had no cans strapped on the side when he left. This is empty now.'

'Perhaps there was an accident when he was refilling the main tank.'

Then where's the body?'

'As I say – the other truck rescued him.'

Byrne stood back and looked at the Land-Rover, then talked more to himself than to me. 'Let's see; twenty-eight gallons in the main tank plus about four in the can – that's thirty-two. He'd need at least twenty to get here, so he was in trouble without a fire – he didn't have enough gas to get back to Tarn. That leaves twelve gallons – eight in the tank and four in this can, I'd say.'

'How do you know the can wasn't empty? He could have refilled his main tank anywhere – even before Assekrem.'

'There's been gas in the can until quite recently – it smells too strong. And when I picked it up the cap was still closed. Now, if that can had been full of gas during the fire it would have exploded – but it hasn't.'

Byrne seemed to be arguing in circles. 'So he put it in the main tank,' I said exasperatedly.

'No,' said Byrne definitely. 'I've seen a lot of burnt-out trucks in the desert, but never one like this – not with all four tyres gone like that, not with so much fire damage up front.' He bent down to examine the petrol tank, and then crawled under.

When he emerged he stood up and tossed something in his hand. 'That was lying on the ground.' It was a small screw cap with a broken wire hanging from it. 'That's the drain cap for the gas tank. The wire which is supposed to stop it unscrewing has been cut. That makes it certain. Someone doused this truck with gas from the can, then decided it would be a good idea to have more. So he drained another four gallons from the tank – maybe eight – to do a really good job of arson. You don't get auto tyres burning all that easily. Then he tossed in a match and went away, and the guy who would do that wouldn't be rescuing Billson.'

'So where's Billson?'

'Don't know. Maybe we'll find his body around here some place.'

I remembered something. 'The man I put on Billson's track back in England seemed to think that someone else was also looking for him.' I frowned. 'And then Hesther Rauhier…' I pulled out my wallet and found the note she had enclosed with the air ticket. I scanned it and handed it to Byrne.

He read it through, then said, 'Know this guy, Kissack?"

'Never heard of him.'

'Neither have I.' He gave me back the note.

'Another thing,' I said. 'Billson might have had a lot of money with him. I think he smuggled it out of the UK.'

'What do you call a lot of money?'

'The thick end of?60,000.'

Byrne whistled. 'I'd call that a lot, too.' He swung around and rooted in the back of the Land-Rover where all that was left of two suitcases were the locks, hinges, metal frames and a pile of ashes. He said, 'Whether Billson's money was in here when the fire bust out we'll never know without a forensic laboratory, and those are a mite scarce around here. Was it common knowledge that Billson would be carrying so much loose dough?'

'I shouldn't think so,' I said. 'It's really only a guess on my part.'

'You don't have a monopoly on guesses,' said Byrne. 'And a lot of guys have been killed for less than that.'

As we walked away from the Land-Rover I said, 'Funny that the chap who did this should close the cap on that empty jerrican; especially as he was going to leave it.'

'Probably automatic,' said Byrne. 'I do it myself. Good habit to have.'

'I'd still like to know what Billson was doing here,' I said.

'He was looking for a wrecked airplane, like you said. And he'd have found it, too – it's about five miles further north of here. I was going to head there if we hadn't found this. Billson must have heard about it back in Tarn so he came for a look-see, the goddamned fool!'

'It couldn't be…' I began.

'Of course it couldn't be his father's plane,' said Byrne tiredly. 'It's a French military airplane that force-landed back when they were getting ready to blow an atom bomb up at Arak. They got the crew out by chopper, then went back to take out the engines and some of the instruments. Then they left the carcass to rot.'

He went to talk to Mokhtar, and I sat on a rock feeling depressed. Billson must have been the biggest damned fool in the history of the Sahara. He had probably read the Land-Rover's Owner's Manual and taken the manufacturer's fuel consumption claim as gospel, but it's one thing tooling along a motorway and another fighting your way through Koudia. I doubt if we'd been getting more than five miles to the imperial gallon since we left Assekrem and perhaps ten or twelve in Atakor. I don't think it's disrespectful to British Leyland to suggest that the Land-Rover was averaging about the same.