A wandering planet from deep space drifts into the solar system and is detected by Earth scientists who soon investigate. The planet is called Medusa; it's surface is uninhabitable and it's people now live in a high-tech underground city. This subterranean society is ruled by women, with men considered inferior. When two Medusian men escape to Earth, Medusa responds by kidnapping two Earth scientists, to be held captive until the return of the escaped men.