The question was so unexpected that I blinked with astonishment and I suppose I was testy. 'What the devil do you mean?'

'I mean put up the price of five camels.'

'How much is a camel worth?' I asked suspiciously. Byrne scratched his jaw through his veil. 'An ordinary pack camel will go for about a hundred pounds sterling. A reasonable Mehari will fetch between a hundred fifty and two hundred.' He laughed. 'You couldn't buy Yendjelan for investigation. The weather was good – no sandstorms.'

'Obsessionally thorough.'

'Yeah,' said Byrne. 'But thorough all the same. Now, when Peter Billson went down it would be likely to be to the north of Agadez, and one thing's for sure – it wasn't in the Air. There are too many people around here and the p lane would have been found. The same applies anywhere north of the Ahaggar. If it went down there it would have been found by some Chaamba bedouin.'

'So that leaves the Ahaggar and you're certain it's not there. You're talking yourself into a corner.'

He said, 'When the French were getting ready to blow that atom bomb at Arak they lost three planes in the Ahaggar. I've told you about one of them. They gave the Ahaggar a real going-over, both from the air and on the ground. They found three planes which was all they expected to find. I'm pretty sure that if Billson's plane had been there the French would have found it.'

'Perhaps they did,' I said. 'And didn't bother to mention it.'

Byrne disagreed. 'It would have made big news. You don't suppose Billson was the only record-breaking airman lost in the Sahara, do you? There was a guy called Lancaster went down in 1933 south of Reggan in the Tanezrouft. He wasn't found until 1962 and it made the headlines.'

I worked it out. 'Twenty-nine years.'

'He was still with the plane, and he left a diary,' said Byrne. 'It made bad reading. Paul knows all about Lancaster; he knows how long a crashed plane can remain undetected here. That's why he thinks he can still find his father.'

'This place where Lancaster crashed – where is it?'

'In the Tanezrouft, about 200 kilometres south of Reggan. It's hell country – reg, that's gravel plain for as far and farther than you can see. I know a bit of what happened to Lancaster because I read about it back in '62 and Paul has refreshed my memory. Lancaster was flying a light plane and 'put down at Reggan to refuel. He took off, got into a sandstorm and tost direction; he flew east damn near as far as In Salah before he put down at Aoulef to find out where he was. He'd intended to fly to Gao on the Niger Bend and that was due south, but he's used up too much fuel so he went back to Reggan. He left next day and after a while his engine quit. So he crashed.'

'Didn't they search for him?'

'Sure they did – by air and ground. I don't know how good their air search was back in 1933, but they did their best. Trouble was they were looking mostly in the wrong place, towards Gao. Anyway, he had two gallons of water and no more, because he had an air-cooled engine. He died eight days later, and was found twenty-nine years later. That's the story of Lancaster.'

'Who found him?'

'A routine French patrol working out of Bidon Cinq. What the hell they were doing in the Tanezrouft I don't know. Probably on a vehicle-testing kick – I can think of no other reason for going into that hell hole.'

'All right,' I said. 'You've made a point. So Peter Billson and his plane can still be in the desert. Are you proposing that we go look for it in this place – the Tanezrouft?'

'Not goddamn likely,' said Byrne. 'I think it possible that Billson went off course. When he disappeared there was a search but, just like Lancaster, he wasn't found because they weren't looking in the right place.'

'And you know the right place, I suppose.'

'No, but think of this. Lancaster's place was found by the French. For all we know it might have been seen much earlier by, say, some Hartani or even a Targui. But why would they want to report it? It would mean nothing to them. Don't forget, this plane crashed only three years after the final battle between the French and the Tuareg when the French got the upper hand at last. The Tuareg felt they didn't owe the French a goddamn thing. Sure, if they'd found Lancaster alive they'd have brought him out, but they wouldn't care much about a dead guy in a dead plane.'

'All right,' I said. 'Spit it out. What are you getting at?' Byrne said, 'Would you put up, say, five camels to help find Paul's old man?'

The question was so unexpected that I blinked with astonishment and I suppose I was testy. 'What the devil do you mean?'

'I mean put up the price of five camels.'

'How much is a camel worth?' I asked suspiciously. Byrne scratched his jaw through his veil. 'An ordinary pack camel will go for about a hundred pounds sterling. A reasonable Mehari will fetch between a hundred fifty and two hundred.' He laughed. 'You couldn't buy Yendjelan for a thousand. Okay, let's say five hundred.'

'You want me to put up?500,' I said carefully. To find Paul's father.'

'I'd put up the same,' he said. 'In camels.'

'So now we have ten camels,' I said. 'How do they help? Do we ride them spaced a hundred yards apart in a sweep of the bloody Sahara?'

'No,' said Byrne calmly. 'They're a reward for a sighting of a plane that crashed in 1936 – payable when we're taken to see it.'

It was a good idea provided I was willing to fork out?500 to help Paul Billson, which wasn't a cast-iron certainty. A good idea but for one thing – the time element. I said, 'For God's sake! How long will it take for news of this reward to get around? Two months? Three months? I don't have that much time to spend here, and if I go, then Billson goes, even if I have to do what Hesther suggested – club him and put him in a sack.'

Byrne laughed quietly. 'You don't know much about the desert. There are trucks going up from Agadez to Tarn every day – two days' journey at the most. Those truck drivers waste no time in sight-seeing; they've seen it already. From Tarn to In Salah – another day. From Agadez east to Bilma -two days. From Bilma to Djanet in the Tassili n' Ajjer – two more days driving fast. In six days minimum I can get news to all the important oases in the desert. The whole Sahara is a big sounding-board if the news is important enough.'

I was sceptical. 'Word of mouth?'

'Word of mouth – hell!' Byrne snorted. 'Ten thousand leaflets handed out. Printed in Arabic, of course. Those who can't read will go to the public letter-writers for a reading as soon as they hear of a ten-camel reward.'

'You're crazy,' I said. I looked around at the thorn trees and the browsing camels. 'Where the blazes are you going to get ten thousand leaflets printed here?'

'I'll draw it up tonight,' he said. 'Then have them Xeroxed m Agadez. They have a machine in the bank.' He leaned forward and peered at me. 'Something the matter?' he en-quired gently.

'No,' I said weakly. 'Nothing the matter. It's just the idea of blanketing the Sahara with leaflets seems a bit weird. You've never worked for J. Walter Thompson, have you?'

'Who's he?'

'A small advertising agency back in the States – and elsewhere.'

'Never heard of him.'

'If you ever leave the desert I'd apply for a job with him. You'd do well.'

'You're nuts!' he said. 'Well, what about it?'

I started to laugh. Between chuckles I said, 'All right… HI do it… but it won't be for Paul Billson. It'll be worth it just to say I've done a saturation advertising campaign in the Sahara.'

Byrne wagged his head. 'Okay – I don't care why you do it so long as you do it.'

'What do I do?' I said. 'Give you a cheque?'

'Now what in hell would I do with a cheque?' he asked. 'I'll put up your half and you get the cash to Hesther in Algiers as and when you can.' He paused. 'Pity we don't have pictures of the plane. Paul had some but they went up with the Land-Rover.'