“What happened? When you looked like that, when you fell…”

“Take two swallows, no more,” he said, holding the open canteen to her mouth. “Just summer change, that’s all. It happens to us every year on Anvhar—only not that violently, of course. In the winter our bodies store a layer of fat under the skin for insulation, and sweating almost ceases completely. There are a lot of internal changes too. When the weather warms up the process is reversed. The fat is metabolized and the sweat glands enlarge and begin working overtime as the body prepares for two months of hard work, heat and little sleep. I guess the heat here triggered off the summer change early.”

“You mean—you’ve adapted to this terrible planet?”

“Just about. Though it does feel a little warm. I’ll need a lot more water soon, so we can’t remain here. Do you think you can stand the sun if I carry you?”

“No, but I won’t feel any better staying here.” She was light-headed, scarcely aware of what she said. “Keep going, I guess. Keep going.”

As soon as she was out of the shadow of the rock the sunlight burst over her again in a wave of hot pain. She fell unconscious at once. Brion picked her up and staggered forward. After a few yards, he began to feel the pull of the sand. He knew he was reaching the end of his strength. He went more slowly and each dune seemed a bit higher than the one before. Giant, sand-scoured rocks pushed through the dunes here and he had to stumble around them. At the base of the largest of these monoliths was a straggling clump of knotted vegetation. He passed it by—then stopped as something tried to penetrate his heat-crazed mind. What was it? A difference. Something about these plants that he hadn’t noticed in any of the others he had passed during the day.

It was almost like defeat to turn and push his clumsy feet backwards in his own footprints; to stand blinking helplessly at the plants.