'This ain't too bad,' he said. 'At least you can stop without getting into trouble. Fech-fech is the worst.'

'What's that?'

'Sometimes you get times of high humidity – high for the desert, anyway. At night in winter the moisture freezes out of the air and forms dew on the surface of the sand. That makes a hard crust on the top with soft sand underneath. Driving on that is okay if you keep moving, but if you stop you're likely to break through and go down to your axles.' He paused and said reflectively, 'Don't bother a camel none, though.'

Another time he said, 'A few years ago I was up north, round about Hassi-Messaoud where the oil-wells are. I came across a big truck – could carry a hundred tons. Russian, it was; used for carrying oil rigs about. The guys who were driving it were Russians, too, and they showed me how it worked. It had eight axles, sixteen big balloon tyres and you could let air out and pump air in by pressing buttons in the cab. They reckoned that with a full load they could jiggle things so that the weight on the ground per square inch was no more than that of a camel. A real nice toy it was.'

'Ingenious.'

'Yeah.' He laughed. 'But they were sloppy about it. They had five of the tyres on wrong way around. Anyway, a few weeks later I heard what happened to it. They were driving along and decided to stop for the night. So they stopped, had something to eat, and went to sleep. But they stopped on fech-fech and during the night the truck broke through. The Russians were sleeping underneath it and it killed them both. They never did get it out.'

A nice illustrative and macabre story of the dangers of the desert. Byrne said, 'Lousy stinkpots! Never have liked them except when I'm in a hurry, like now.'

After a while the sand dunes levelled off into a plain of sand, and presently Byrne said, 'The Tree!' On the far horizon ahead was a black dot which might well have been an optical illusion – a speck of dust on the eyeball – but which proved to be a solitary wide-spreading thorn tree. There was a well near the tree and the ground all about was Uttered with the olive-shaped pellets of camel dung. There were also several skeletons of camels, some still covered with hide, mummified in the dry, hot desert air.

Byrne said, 'We'll stop here for something to eat – but not near the well. Too many biting bugs.'

As we drove past, Paul, behind me, said, 'There's someone standing by the tree.'

'So there is,' said Byrne. 'Just one man. That's unusual here. Let's go see who he is.'

'He pulled over the wheel and we stopped just by the tree. The man standing there was not a Targui because he wore no veil and his skin was darker, a deep rich brown. He was shorter than the average Targui and not as well dressed. His gandoura was black and his head cloth in ill array.

Byrne got out and talked to the man for a few minutes, then came back to the truck. 'He's a Teda from the Tibesti. He's been hanging around here for three days waiting for someone to come along. He's heading east and he can't do the next stretch alone.'

'How did he g et here?'

'Walked. Only just made it, too. Did the last two days without water. Do you mind if we give him a lift as far east as we're going?'

It's your truck,' I said. 'And you're the boss.'

Byrne nodded and waved to the man, who came over to the Toyota. He was carrying a shaggy goatskin bag which Byrne said was a djerba, used for holding water. Byrne tapped the bag and asked a question, pointed to the well. The man answered and then, at a command from Byrne, emptied the contents of the bag on the ground.

'It's okay to drink that stuff if you have to,' said Byrne. Hut not unless. An addax antelope fell into the well a few years ago and it's been no goddamn good since.'

As we drove away I said, 'What's his name?'

'He didn't say. He said his name used to be Konti.'

I frowned. 'That's a funny thing to say.'

'Not really,' said Byrne. 'It means he's a murderer.' He seemed unperturbed.

I twisted around to look at the man in the back of the truck, whose name used to be Konti. 'What the hell…'

'It's okay,' said Byrne. 'He won't kill us. He's not a professional murderer. He probably killed somebody in a blood feud back home and had to take it on the lam. Maybe he reckons it's now safe to go back or he's got word his family has paid the blood money.'

He stopped the truck about a mile the other side of the Tree. 'This will do.' We got out. From the back of the truck Byrne took what appeared to be a length of metal pipe. 'Help me fill this.'

There was a brass cap on the top which he unscrewed. I held a funnel while Byrne filled the contraption with water from a jerrican. As he did so he said, 'This is a volcano – the most economic way of boiling water there is.'

It was simple, really, consisting of a water jacket, holding about two pints, around a central chimney. Byrne poked a lighted spill of paper into a hole in the bottom, added a few twigs of acacia and, when the fire had taken hold of those, popped in a handful of pellets of dried camel dung which he had picked up near the tree. They burned fiercely, but with no smell. Within five minutes we had boiling water.

We lunched on bread and cheese and mint tea, our murderer joining in. 'Ask him his name,' I said. 1 can't keep on referring to him as the man who used to be Konti.'

As Byrne talked to the man Paul said, 'I'm not going to ride with any murderer. Nobody asked me if he could come along.'

Byrne stopped abruptly and turned to Paul. Then you'll walk the rest of the way, either forward or back.' He jerked his head. 'He's probably a better man than you. And the reason you weren't asked is that I don't give a good goddamn what you like or what you don't like. Got it?' He didn't wait for a reply but went back to talking in guttural tones.

I looked at Paul, whose face was as red as a boiled beet. I said softly, 'I told you to walk carefully around Byrne. You never learn, do you?'

'He can't talk to me like that,' he muttered.

'He just did,' I pointed put. 'And what the hell are you going to do about it? I'll tell you – you're going to do nothing, because Byrne is the only thing standing between you and being dead.'

He lapsed into a sulky silence.

Byrne finished his interrogation and turned back to me. 'He says it's okay for you to call him Konti now. I don't speak his lingo well, but he has some Arabic – and I was just about right. He killed a man three years ago in the Tibesti and ran away. He's just learned that the blood money has been paid so he's going back.' He paused. 'Blood camels, really; there's not much hard cash in the Tibesti.'

'How many camels are worth a man's life?'

'Five.'

'Half a 1930s aeroplane,' I commented.

'You could put it that way,' he said. 'The change of name is a pure ritual, of course. You know what he'd do when he ran away? He'd kill an antelope, take a length of its large intestine, and pull it on to his feet like socks. Then he'd jump up and down till it broke. Symbolic breaking of the trail, you see.'

'Weird,' I said.

'Yeah; funny people, the Teda. Related to the Tuareg but a long ways back.' He looked up at the sun. 'Let's go. I want to be the other side of Fachi before nightfall.'

We pressed on and entered an area where again there were large dunes, some of them several hundred feet high. I realized that Byrne was doing all the driving and offered to spell him but he rejected the idea. 'Later, maybe; but not now. You'd get us stuck. There's an art in driving in soft sand, and you have to hit these rises at just the right angle.' Once I glimpsed an animal with large ears scurrying over the edge of a dune. Byrne said it was a fennec. 'Desert fox. Gets its moisture from eating insects and jerboas. Jerboas make water right in their own bodies. Least, that's what a guy told me who was out here studying them. That fennec wouldn't show himself in daytime in summer; too goddamn hot.'