There are police posts on all the main tracks out of Tarn and when he didn't show up at any of those they'd be sure. So when he shows up in Tarn he'll be arrested.'

'At least he'll get hospital treatment,' I said. 'And when he's out of hospital I'll stand bail.'

'You'll be lucky,' said Byrne drily. 'Because this guy is going to show up with a bullet hole in him and Algerian cops are no different than any other cops – they don't like mysterious bullet wounds. It's going to be a mess.'

He held up a finger. 'One – Billson has broken the law, and it's a serious offence. The Algerians are nuts on security and they don't like foreign nationals floating around the desert tribes unobserved. That could mean prison and I wouldn't wish my worst enemy in an Algerian prison.' A second finger joined the first. 'Two – he comes back with a bullet wound and that the cops won't like either. It's not an offence to be shot but it means someone else ought to be in jail, and that means trouble where there ought to be no trouble.' A third finger went up. 'Three – the guy who was shot is a foreigner and that brings Algiers into the act complete with a gaggle of diplomats. As far as I know Britain broke off diplomatic relations with Algeria years ago. I don't know who represents British nationals here – could be the Swiss – but that means a three-cornered international hassle, and no one is going to like that.'

'I begin to see the problems,' I said thoughtfully.

'Four,' said Byrne remorselessly. 'And this is the big one. Supposing we take Billson into Tarn and he goes into hospital. It's only a small place and within twelve hours everybody is going to know about the man in hospital who was shot -including the guy who shot him

…'

'… and who thinks he's dead,' I chipped in.

'… and whom Billson can identify. What's to stop him having another crack and finishing the job?'

'If he's still around.'

'What makes you think he won't be?' Byrne stood up and looked down at Billson. 'This guy is giving everybody a pain in the ass – including me.' He shook his head irritably.. 'If it wasn't for Hesther

…' His voice tailed away again.

'Is there an alternative to Tarn?'

'Yeah.' He kicked at the sand. 'But I'll have to think about it.'

He went over to the truck and came back with the rifle, then spoke to Mokhtar who took a full magazine from the pouch hung on his neck. Byrne slipped it into the rifle with a metallic click, worked the action to put a bullet up the spout, and carefully set the safety-catch. 'I suppose you know how to use one of these, Colonel, sir?'

'I have been known to.'

'You might have to use it. It shoots a shade to the left and upwards; say, two inches at ten o'clock at a hundred yards. We'll stand watches tonight.'

I frowned. 'Expecting trouble? I'd have thought…'

He broke in. 'Not really, but Billson will have to be watched throughout the night.' He held up the rifle. 'This is for unexpected trouble.'

I stood the middle watch in order to give both Byrne and Mokhtar an uninterrupted run of sleep; I didn't know where we were going if it wasn't Tammanrasset, but wherever it was they would have to take me there, so they were more important than me.

Billson was unmoving but still breathing, and I thought he looked a shade better than he had. For one exasperated moment that evening I had thought of quitting and going back to London. As Byrne had said – though less politely -Billson was nothing but trouble for everyone who came near him, and I did think of leaving him to stew in his own juice.

But the thought of going back and telling Alix Aarvik about all this made my blood run cold. Besides, it wouldn't be fair on Byrne and Mokhtar who had gone to a great deal of trouble to help a man they didn't know. Also, I would have to be on hand when Billson recovered because someone had to get him out of the country as he had very little money left. And London was far away and receding fast, and I found I quite enjoyed the desert in a masochistic way.

I took the rifle and looked at it in the dim light of the fire. It was an old British Lee-Enfield. 303 and, judging by its low number, it had seen service in the First World War, as well as the Second. I took out the magazine and worked the action to eject the round in the breech, then looked down the barrel into the fire. It was as clean as a whistle and any hardened sergeant would have had to give Mokhtar full marks. He had looked after it well. I reloaded and laid the rifle aside, then checked Billson again.

Towards the end of my watch he began to stir and, just before I woke Byrne, he had begun to mutter, but his ramblings were incoherent. I put my hand to his brow but he did not seem to be running a temperature.

I woke Byrne. 'Billson's coining to life.'

'Okay; I'll tend to him.' Byrne looked at the sky to get the time. He wore no watch. 'You get some sleep. We start early; our next camp is at Abalessa.'

I wrapped myself in my djellaba because it was very cold, and lay down. I wasted no time wondering about Abalessa but fell asleep immediately.

Billson was obviously better in the morning, but he was dazed and I doubt if he knew where he was or what was happening to him. We bedded him down in the back of the Toyota on the camel hair cloth that had served as a windbreak and on a couple of djellabas. 'We can get some camel milk once we're out of Atakor,' said Byrne. 'And maybe scare up some hot soup. That'll bring him around better than anything else.'

We travelled fast because Byrne said we had a long way to go. Coming out of Atakor we encountered the Tuareg camp we had passed on the way in. They were packing up to go somewhere but found some warm camel milk for Mokhtar. Byrne had thrown a djellaba casually into the back of the truck, covering Billson, and stood guard. 'There's no need for anyone to see him.'

We left the camp and stopped for a while a little later while we spooned milk into Billson. He seemed even better after that, even though the skin was peeling from his face and the backs of his hands in long strips. Mokhtar applied more salve and then we set off again, with Byrne really piling on the speed now that the country was much better.

These things are relative. Coming from the green land of England, I would have judged this place to be a howling wilderness. All sand, no soil, and the only vegetation an occasional clump of rank grass and a scattering of thorn trees which, however desirable they may have been to a camel, did nothing for me. But I had not just come from England; I had come from Koudia and Atakor and what a hell of a difference that made. This country was beautiful We travelled hard and fast, making few stops, usually to top up the tank with petrol from the jerricans. Billson finished the milk and was able to drink water which put a bit more life into him, although he still wandered in his wits – assuming he had any to begin with. Once Byrne stopped and sent Mokhtar on ahead. He disappeared over a rise, then reappeared and waved. Byrne let out the clutch and we went a head at a rush, topping the rise and down the other side to cross what, for the Sahara, was an arterial highway.

'The main road north from Tarn,' said Byrne. 'I'd just as soon not be seen crossing it'

'Where are we going?'

'We're going round Tarn to the other side – to Abalessa.' He fell silent and concentrated on his driving.

Abalessa, when we got there, was a low hill on the horizon. We didn't drive up to it but made camp about a mile away. There was still some gazelle meat left so Mokhtar seethed it in a pot to make soup for Billson before putting on the kettle for the mint tea. Byrne grunted. 'You can have your coffee when we go into Tarn tomorrow. Me, I'm looking forward to a cold beer.'

'But I thought…'

'Not Billson,' said Byrne. 'He stays here with Mokhtar. Just you and me. We've got to make you legal.'