An international agency, COSMOS, is in charge of space exploration in the not very distant future. Odd forms of life have been discovered on Mars, Venus, and Jupiter; there may be a life form on Mercury; and finally something utterly mystifying is discovered on the moon. Three astronauts land and examine an installation that all three perceive as radically different - one sees a heap of gold, one a fort bristling with guns, one a space platform and space craft. They return to Earth with some crystals picked up at the mystery site.

All three soon produce children - the moon children, gifted, precocious, and seemingly damned by the crystals their fathers had handled. Two are eerily beautiful, the third a grotesque monster. And the three soon discover that they are Earth's hope for survival, as interplanetary invasion brings overwhelming alien forces to bear on mankind.