'Not surprising, after forty-two years. What are you really getting at, Luke?'

'You can bet your last cent that Billson would have had his compass checked out real good before the race. His life depended on it.'

'And it let him down.'

'Yeah; but only after Algiers. And compasses don't go fourteen degrees wrong that easy.'

I stared at him. 'Sabotage!'

'Could be. Can't think of anything else.'

My thoughts went back to English, the journalist who had set fire to Paul. 'That idea has come up before,' I said slowly. 'A German won the race – a Nazi. I don't suppose he could have done it personally, but a friend of his might.'

'I'd like to take this compass out,' said Byrne. 'There's a screwdriver in that kit of tools I brought.'

'I wondered about that,' I said. 'Were you expecting this?'

'I was expecting something. Don't forget there's a son of a bitch who is willing to kill to prevent this plane being found.'

'I'll get the screwdriver.'

As I dropped to the ground Byrne said, 'Don't tell Paul.'

Paul was sitting on the ground in front of Flyaway just looking at her. I walked away, got the screwdriver and came back, concealing it in the folds of my gandoura. Byrne attacked the first of the four screws which held the compass in place. It seemed locked solid but an extra effort moved it and then it rotated freely.

He took out all four screws and gently eased the compass out of place and turned it over in his hands. 'Yeah,' he said. 'You see these two brass tubes here? Inside those are small pole magnets. This screw here makes the tubes move like scissor blades – that's how the compass adjuster gets his results. And this is a locking nut to make sure the tubes can't move once they're set'

He tested it with his fingers. 'It's locked tight – which means…'

'… that if the compass is fourteen degrees out of true it was done deliberately?'

'That's right,' said Byrne.

CHAPTER TWENTY-EIGHT

Sabotage! An ugly word. An uglier deed.

I said, 'How long would it take to do it?'

'You saw how easy it was to take out this compass. To make the change and put bac k the compass wouldn't take long. A maximum of fifteen minutes for the whole job.'

'I'm taking that compass back to England with me,' I said. 'Just as it is. I'm beginning to develop peculiar ideas.'

'It only tells half the story,' said Byrne. 'We have to solve the other half – why did he come down? I have ideas on that. I want to look at the plumbing of this airplane.'

'I'll leave you to it.' I climbed down from the wing and joined Paul. 'Well, Paul, this is it – journey's end.'

'Yes,' he said softly. He looked up. 'He wasn't a cheat That South African was lying.'

'No, he wasn't a cheat.' I certainly wasn't going to tell Paul that the compass had been gimmicked – that would really send him round the twist. I said carefully, 'Byrne is trying to find out what was wrong with Flyaway to make her come down. Do you mind?'

'Of course not. I'd like to know.' He rubbed his shoulder absently. 'That newspaper back in England. Do you think the editor will publish an apology?'

'An apology? By God, Paul, it'll be more than that. It will be headline news. There'll be a complete vindication.' But it would be better if we could find the body, I thought.

I looked around and tried to put myself in Billson's place. He had either tried to walk out or he hadn't, and both Paul and Byrne were fairly certain that he'd do the right thing and stick close to Flyaway; it was standard operating procedure. He must have known that an air search would be laid on and that an aeroplane is easier to spot than a man on foot. What he didn't know was that no one dreamed of searching the Tassili area.

So if he hadn't walked out where was he? Atitel had said he hadn't seen a body, but had he searched?

I said nothing to Paul but walked away and climbed the side of the fallen rock pillar from which I first saw Flyaway, and began to walk along it. It was my idea that Billson would want to get out of the sun, so I was looking for a cave.

I found the remains of the body half an hour later. It was in one of the shallow scooped-out caves peculiar to the Tassili and the walls were covered with paintings of men and cattle and hunting scenes. I use the word 'remains' advisedly because scavengers had been at the body after Billson had died and there were pieces missing. What was left was half covered in blown sand, and near by was the dull gleam of a metal box which could have been a biscuit tin.

I touched nothing but went back immediately. Paul hadn't moved but Byrne was on top of Flyaway and had opened some kind of a hatch on the side of the fuselage. As I climbed up he said, 'I think I've got it figured.'

'Never mind that,' I said. 'I've found the body.'

'Oh!' He turned his head and looked at Paul, then turned back to me. 'Bad?'

'Not good. I haven't told Paul yet You know what he's like.'

'You'll have to tell him,' said Byrne definitely. 'He'll have to know and he'll have to see it. If he doesn't he'll be wondering for the rest of his life.' I knew he was right. 'But don't tell him yet. Let's get this figured out first.'

'What have you found?'

'If you look in the cockpit you'll see a brass handle on the left. It's a sort of two-way switch governing the flow of gas to the engine. In the position it's set at now it's drawing fuel from the main tank. It was in that position when I found it. Turn it the other way and gasoline is drawn from an auxiliary tank which has been built into the cargo, space here. Got the picture?'

'He was drawing from his main tank when he crashed.'

'That's it.' He fumbled in his gandoura and came out with the photocopies I had given him. 'According to this, the main tank holds 334 gallons which gives a range of seventeen hundred miles at three-quarters power – that's cruising. But Billson was in a race – he wouldn't be cruising. I reckon he'd be flying on ninety per cent power, so his range would be less. I figure about fifteen hundred miles. It's eighteen hundred from Algiers to Kano, so that's a shortfall of three hundred miles.'

'Hence the auxiliary tank.'

'Yeah. So he needs another three hundred miles of fuel -and more. He'd need more because he might run into head winds, and he'd need a further reserve because he wouldn't want to do anything hairy like finding Kano in the dark and coming in on his last pint of gas. At the same time he wouldn't want this auxiliary tank to be full because that means weight and that would slow him down. I've been trying to figure like Billson and I've come up with the notion that he'd put a hundred fifty gallons in this tank. And you know what?'

'Tell me.'

'That's just about enough to bring him from Algiers to here on the course he was heading.'

'You mean when he switched over from the auxiliary to the main tank his engine failed. Empty main tank?'

'Hell, no! Billson wasn't an idiot – he'd supervise the filling himself. Besides, there are gauges in the cockpit. The engine quit all right, but it wasn't because the tank was empty. I'd like to find out why.'

'How?'

'I'd like to open up the main tank. Think Paul would mind?'

'I'll ask him.'

Paul said he didn't mind; in fact, he developed an interest as Byrne stood with hammer in one hand and cold chisel in the other surveying Flyaway. 'I've been tracing the gas lines and I'd say the main tank is in this mid-section here – might even extend into the wing fillets. I'll start there.'

He knelt down, laid the cutting edge of the chisel against the fuselage, and poised the hammer. 'Wait!' said Paul quickly. 'You might strike a spark.'

Byrne turned his head. 'So?'

'The petrol…'