A group of astronauts embarks on a mission to Mars but are unexpectedly hurled through a time warp, crash-landing on a post-apocalyptic future Earth. The planet is now inhabited by two factions: a primitive, mutated surface-dwelling species and an advanced, civilized society living underground. As they struggle to comprehend their new reality, the astronauts discover that the surface mutants are plagued by radiation from a long-past nuclear war, while the subterranean people have maintained some semblance of human culture and technology.

The astronauts face the challenge of surviving in this hostile environment and are soon caught between the two factions. The tension escalates as they grapple with complex moral choices and alliances, attempting to aid the underground society while dealing with the ever-present threat from the mutants. As their loyalty is tested and resources become scarce, the astronauts must find a way to safeguard humanity's future in this strange and perilous world.