Byrne came back on foot. 'I've put the truck where it won't be found easily. Let's move.'

I drew him on one side. 'Have you been up there before?'

'Sure. I've been most places.'

'What's the travelling like once we get on top?'

'Not bad – if we stick to the water-courses.'

'Water-courses!' I said incredulously.

'You'll see,' he said with a grim smile. 'It's the damnedest country you're ever likely to see. Like a maze – easy to get lost. What's your point?'

'I'm thinking of Paul.'

Byrne nodded. 'Yeah, he's been on my mind, too. But if he can get to the top here he'll be okay.'

'Tassili n' Ajjer,' I said thoughtfully. 'What does that translate as?'

'The Plateau of Goats – not that I've ever seen any. A few wild camels, though.' He shook his head irritably. 'Let's move, for God's sake!'

And so we started. It wasn't bad at first because we were on gently rising ground approaching the base of the cliffs. When we got to the ravine it was bigger than it looked at first, maybe half a mile wide at the bottom and narrowing as it rose. There was a path of sorts which zig-zagged from side to side so that for every hundred yards of forward travel we walked perhaps six hundred. And climbed, of course, but not as much.

It was a steady toil which put a strain on the calf muscles and on to the heart and lungs, a battle for altitude. It wasn't any kind of a mountaineering feat, just damned hard work which went on and on. There was no sound but the steady rasping of breath in my throat, the occasional clatter as a stone was dislodged to go bounding down the ravine, and the clink of a jerrican as it hit a rock. Sometimes a donkey would snort but no one had breath for talking.

I think we would have made the top quicker had it not been for Paul who held us back. We stopped frequently for him to catch up, and waited while he rested. It gave me time to rest my own lungs, for which I was thankful. Atitel and Hami didn't seem worried by the effort; they would smoke a half-cigarette and carefully put away the stubs before resuming the climb. As for Byrne, he was all whipcord and leather, as usual, but his nose was beakier and- his cheeks more sunken than I had noticed before.

So it was that it took us over four hours to climb two thousand feet and I doubt if the ground distance we had covered would be more than a mile and a half when measured on a map. As soon as the ground began to level we stopped and within minutes Atitel and Hami had the inevitable miniature Tuareg camp fires going and water on the boil to make tea. I said breathlessly, 'Are we there?'

'Nearly. The worst is over.' Byrne pointed towards the setting sun. 'I reckon you can see over eighty kilometres from here.'

The view was fantastic – dun-coloured hills close by changing to blue and purple in the distance. Byrne pointed towards a jumble of dunes. 'The Erg d'Admer; all that sand was washed down from the plateau. Must have been one of the biggest waterfalls in the world right here – a fall of two thousand feet.'

'Waterfall!' I said weakly.

'Sure; the Tassili was well watered at one time. Real big rivers. And it was good cattle country with plenty of feed. Long time ago, of course.'

Of course!

I sipped sweet tea from a small brass cup and regarded Paul, who was lying flat on his back and seemed completely exhausted. He'd made it but only just. I went over to him. 'Have some tea, Paul.'

His chest heaved. 'Later,' he gasped.

'Max!' said Byrne. His voice was soft but there was a snap of command in it. I looked up and he jerked his head so I went and joined him where he stood looking down the ravine.

He pointed to the desert floor and there, two miles away and nearly half a mile below was a movement of sand.

'Dust devils?' They were familiar in the desert; miniature whirlwinds caused by the convection currents stirred up by the heat.

Byrne looked up at the sun. 'Not at this hour. I think we've got company. There are two.'

'How the hell would Lash know we came here?'

Byrne shrugged. 'Anyone going up to the Tassili from Djanet would com e this way. No other way as easy.' Easy! 'He'll have been asking around in Djanet; it would have been no trick to trace us – just a few enquiries at the hotel.'

'We ought to have been more discreet.'

'It wouldn't have worked. No one can hire men and animals in Djanet without the word getting round. Lash's men might speak Tamachek, but even if they have only Arabic they'd have no trouble in finding out what they wanted to know.'

I looked down the cliffside and there was no movement to be seen. 'So we're in trouble.'

'Not too much,' said Byrne unperturbedly. They won't climb up here in the dark, and the sun will set in an hour. I guess they'll wait until tomorrow. That gives us a chance to get lost.' He looked back at Paul. 'We'll give him time to rest up then push on.'

'Where to?'

'Over the rise there – to Tamrit and Assakao.'

Never could I have imagined a landscape such as that of the Tassili n' Ajjer. We walked in the beds of long-gone rivers which, when in flood, had carved deeply into the soft sandstone, making what were now canyons, the walls of which were scalloped into whole series of shallow caves on all sides. When desiccation set in and the water had gone the wind had continued to work on the Tassili, abrading the sandstone for thousands of years and sculpturing the rock into pillars and pinnacles of fantastic shape, some towering two hundred or more feet, others undercut at the base and felled as a woodsman would fell a tree.

The land had a baked appearance like an ill-made pie left too long in the oven and, indeed, the Tassili had been under the furnace of the sun for too long without the amelioration of vegetative cover. The sandstone was blackened and covered with a patina of what Byrne called desert varnish. 'You get dew on the stone some nights,' he said. 'And it draws iron and manganese to the surface. Next day the dew evaporates and the iron and manganese oxidize. Have that happening for a few hundred or thousand years and you get a good coating of varnish.'

As he had said, it was a maze, the canyons that had been water-courses joining, linking and separating. I had the feeling that this had been some sort of delta, the end of a journey for a mighty river, once fast but now slow and heavy with silt like the delta of the Nile. But then it had come to Tamrit and the edge of the Tassili to plunge two thousand feet to the land below, taking the silt to what were now the huge dunes of the Erg d'Admer. And now there was no water. The land was dry as a camel bone found in the Tenere, but not bleached – rather sun-scorched and hardened like a mummified corpse.

That I saw during the first hour before the sun set and then, at Byrne's insistence, we continued, aided by the lamp of a full moon, until nine that night when he relented and we made camp. By this time. Paul was near collapse and I was wearier than I'd been since our stroll through the Tenere. Too tired to eat, I crawled into one of the shallow caves in the rock and fell asleep huddled in my djellaba, I awoke in daylight to find a man looking down at me. He was dark-skinned and wore nothing but a loincloth and, in his right hand, he carried a spear. Behind him was a herd of cattle, healthy-looking beasts with piebald hides and wide-spreading horns. And beyond them was a group of hunters carrying bows, some with arrows nocked to the string.

I blinked in surprise and sat up and stared. The man was nothing but paint on the wall of the cave, and so were the cattle and the hunters. I jerked my head around and saw Byrne squatting outside the cave, feeding the water-boiling contraption he called a volcano. Behind him Hami was loading djerbas on to a donkey.

'Luke,' I said, 'have you seen this?'