A husband and wife team are escorting a young woman to a planet; all planets are first colonised by men, and when it is deemed safe, one woman is sent. If she can safely have normal children, the planet is opened up for colonisation.

Most of the story/novella is set on the ship, with her arrival being the climax; and all the male colonists greeting her with jubilation. It's an honour to be chosen, but the husband and wife are sorry for her; as she doesn't realise that she is the final "proof" of the planet being safe to colonise or not.