The last survivor of a spaceship that crash lands on Mars finds a deserted Martian village. Natives of the Andes Mountains are able to survive in the thin atmosphere of Mars without pressure suits, to the great resentment of those born at sea level. A human and an ezwal, a large, blue, three-eyed being with the power of telepathic communication, crash land on a jungle planet and are forced to cooperate with each other to stay alive--despite the fact that the ezwal hates humans and would just as soon tear the human into little pieces. A creature, actually the galaxy's greatest mathematician, is held in a huge vault on Mars that is made of ultimate metal and whose time-lock is keyed to the ultimate prime number.