Cycle of fire

Hal Clement

After his ship crashed on the inhospitable planet Abyorman, Nils Kruger had spent weeks wandering across the face of the planet.suffering from blistering heat, the searing cold of an alien climate. Now he had found a fellow wanderer, Dar, an alien castaway. They may both die. The human opts to do something about it. Dar, who knows the time of his death in advance, opts to do nothing. Which of them is right? Perhaps both