On Mars, Ylla (a Martian woman trapped in an unromantic marriage) dreams of the coming astronauts through telepathy. Her husband, though he pretends to deny the reality of the dreams, becomes bitterly jealous, sensing his wife's inchoate romantic feelings for one of the astronauts. He kills the two-man expedition, astronauts Nathaniel York and Bert Conover, as soon as they arrive. Mission control on Earth does not know the fate of the crew, and one of the senior astronauts Jeff Spender urges the project director Col. John Wilder to abandon the Zeus project because of concerns that Mars may already harbor life. Wilder (who has shepherded the project for ten years) refuses, among other things because he believes mankind might escape environmental pollution and war on Earth by colonizing Mars instead.