And felt his foot fall into empty space.

Off balance, he teetered on the brink of the wadi bank, Flailing his free arm in the air to try to regain his stance. His whirling arm struck Tug across the nose and the little horse reared back in surprise and alarm, unsighted by the cloying sand around his eyes and not seeing where the blow had come from.

Will began to fall and desperately threw himself back from the wadi's edge.

The reins came loose from his grip as Tug jerked away, terrified by the thundering noise of the wind, startled by the sudden, unexpected blow across his muzzle and panic-stricken by the loss of contact with his master. Blinded by the sand, he wheeled instinctively away from the wind, seeking for some sense of Will in the storm close by him. But his senses, normally so keen and finely honed, were deadened by the all-pervading scream of the storm, the heat and the whipping, flying sand. Still trying to make some contact with Will, he took a pace, then another, whinnying shrilly in alarm. But he was already heading in the wrong direction.

Will floundered to his feet. He tried to call to his horse but his voice was barely a croak now. He thought – thought – he could sense a presence in the storm a few metres away. He stumbled towards it, knowing it was Tug.

But the vague shape, nothing more than a half-perceived denser mass in the darkness surrounding him, moved away and he lost sight of it. He stumbled forward, the wind behind him now.

'Tug!' he tried to shout. But the sound was inaudible even to his own ears, drowned by the triumphant shriek of the massive wind. He stretched out a hand but, touched nothing but flying sand.

Then, miraculously, he saw a shadow looming out of the dark mass of wind and sand and debris.

'Tug!' he gasped. But a hand grabbed the collar of his cloak and pulled him forward.

Dimly, he realised that he was face to face with Selethen.

'Get… down!' the Wakir shouted at him, dragging him towards the rough ground. Will fought against the iron grip.

'Horse… ' He managed to force the word out. 'My horse… '

'Leave… him!' Selethen spoke slowly and deliberately so that he could be heard above the storm. Now he was urging his own horse, trained for and accustomed to these conditions, to its knees, all the time holding Will's collar with his free hand. The Arridi horse lay on its side, head curled round into the shelter of its own body. Will felt a foot slip between his feet to trip him and he and Selethen crashed to the ground together, the Arridi dragging him into the scant shelter provided by the horse's body.

'Tug!' Will screamed, the effort searing his parched throat with agony. Selethen was fumbling with his cloak, trying to drag it over both their heads to protect them from the sand. He leaned over to speak directly into Will's ear.

'You'll die out there!' he shouted. 'You'll never find him now. Try to do it and you'll die! He's gone! Understand?'

Dully, Will realised that he was right. He would have no chance of finding his horse in the blinding, whirling mass of sand that surrounded them. He felt a great stab of pain in his heart at the thought of his horse – alone and terrified in all that horror – and he sobbed uncontrollably, great racking sobs that heaved and shuddered through his entire body.

But there were no tears. The heat and the choking, cloying sand and dust denied him even that small comfort.

The storm passed over them. Will had no idea how long it battered them, screamed at them, tortured them. It must have been hours. But eventually it passed.

While it raged around them, it was as if his senses shut down so that he was conscious only of the screaming, tormenting voice of the wind. In the sudden silence that greeted its passing, he became aware of other sensations. There was something heavy across his legs and body, and on top of the cloak that Selethen had pulled over their heads. He felt Selethen moving and he wriggled, fighting against the constricting weight as well, realising it was sand piled up on them, thrown there by the rampaging wind.

Selethen coughed beside him and managed to throw a corner of the cloak clear. Dirty yellow-brown sand cascaded in on them both. Will rolled to his back and shoved the cloak away from his own face, managing to look down at himself.

There was no sign of his body or legs. There was,,nothing but a sand-covered hump. He struggled to sit up, shovelling the sand away from his lower body with his hands. Beside him, he was conscious of Selethen doing the same thing.

The earth seemed to move behind him and he twisted round, startled, in time to see Selethen's horse rolling and heaving to get its feet under it. The stallion forced its way upright, sending a huge weight of sand crashing onto the two men who had sheltered behind him. Then, upright, the horse shook itself mightily and more dirt flew.

Will heaved himself backwards into the clear space left by the horse's body and felt his legs coming free. With a final effort, he broke clear of the sand's grip and staggered to his feet.

Below them, in the wadi bed, others were doing the same. He could see movement in the rows of piled sand that marked where the others had sheltered. Then the sand surface heaved in a score of places, as if in response to some minor earthquake, and bodies began to break clear. Sheltered by the bank, the others had fared better than he and Selethen. The covering of sand that lay across them was not so deep or heavy. But it still took some effort to break clear. The horses, able to stand tail on to the wind and sheltered by the wadi bank, were in better condition. At least they hadn't been half buried.

He looked around into Selethen's face. It was coated and crusted with the fine clinging yellow sand. The eyes, ted-rimmed and sore, stared out of it like holes in a grotesque mask. Will realised that he would look no better. The Wakir shook his head wearily. He took a water skin from his horse's saddle bow, wet the end of his kheffiyeh, and began to clean the clogged sand away from the animal's eyes, crooning softly to him. The sight of the horse responding trustingly to his rider's ministrations brought a horrible realisation back to Will and he looked around frantically, hoping against hope that he would see another hump in the sand – a hump that would resolve itself into the shaggy-haired form of Tug as he struggled to his feet. But there was nothing.

Tug was gone.

Gone somewhere out in the wasteland of the desert. Will blundered a few paces away from the wadi's edge, tried to call his name. But the dryness and the sand in his throat defeated the effort and no sound came. A hand touched his shoulder and he turned as Selethen thrust the water skin to him. He took a mouthful, rinsed it and spat. Then another, feeling the warm moisture soak into the soft tissues of his throat.

He realised that Selethen himself hadn't drunk yet and he handed the water skin back to him, watched as he rinsed, spat, then swallowed a mouthful or two himself. Finally, he lowered the skin.

'You… all… right?' he asked haltingly. Will shook his head, pointing vaguely to the desert behind them.

'Tug,' he said miserably. Then he could say no more. He heard boots slipping and sliding in the sand and turned to see Halt climbing wearily up the wadi bank. His face was covered and yellow-crusted as well. His eyes were red-rimmed and sore.

'Are you all right?' he repeated Selethen's question. Then, his eyes darted from side to side and a horrified look came over his face. 'Where's Tug?' he asked fearfully. Will bowed his his head, feeling tears trying to form. But, as before, his body lacked the moisture to allow them.

'Gone,' he said bitterly. He could only manage the one syllable. He waved his hand to the desert.