cried, for the first time exhibiting a sign of nervousness.

"Good heavens, how pleasant! Are we going to be buried under a mound of
sand, like the pictures we used to have in our schoolbooks of caravans
overwhelmed in the Sahara?"

Mrs. Norton smiled.

"Not quite as bad as that," she answered. "But unpleasant enough, I
assure you. If only we had any shelter!"

Wargrave looked around desperately. He had hitherto no experience of
desert country; and the sudden darkness and the grim menace of the
approaching black wall of the sandstorm seemed to threaten disaster. He
saw a thick clump of cactus half a mile away.

"We'd better make for that," he said, pointing to it. "It will serve to
break the force of the wind if we get to leeward of it. Let's mount."

He put her on her horse and then swung himself up into the saddle.
Together they raced for the scant shelter before the dark menace
overspreading earth and sky. The sun was now hidden; but that brought no
relief, for the heat was even more stifling and oppressive than before.
The wind seemed like a blast of hot air from an opened furnace door.

Pulling up when they reached the dense thicket of cactus with its broad
green leaves studded with cruel thorns, Wargrave jumped down and lifted
Mrs. Norton from the saddle. The horses followed them instinctively, as
they pressed as closely as they could to the shelter of the inhospitable
plant. The animals turned their tails towards the approaching storm and