The narrative involves a world where astronauts, known as Spacers, are neutered before puberty to avoid the effects of space radiation on gametes. Aside from making them sterile, the neutering also prevents puberty from occurring and results in androgynous adults whose birth-sex is unclear to others. Spacers are fetishized by a subculture of 'frelks', those attracted by the Spacers' unattainability and unarousability ('free-fall-sexual-displacement complex'). The mischief-loving Spacers exploit this for amusement and money—and possibly out of loneliness and a desire to recapture their lost sexuality.
Frelk is used as a derogatory term by the spacers in the story, who nonetheless engage in prostitution by accepting money to give frelks the pseudo-sexual contact they desire.