Various interconnected people struggle to survive when an earthquake of unimaginable magnitude hits Los Angeles, California.

A young terrorist kills and injures patrons of a Norfolk amusement park by placing homemade explosives on the track of one of its roller coasters. After staging a similar incident in Pittsburgh, he sends a tape to a meeting of major amusement park executives in Chicago, demanding $1 million to make him stop.

After the destruction of the Twelve Colonies of Mankind, the last major fighter carrier leads a makeshift fugitive fleet in a desperate search for the legendary planet Earth. This film is adapted from a television series that aired on ABC from September 17, 1978, to August 17, 1980. The first and fifth episodes of the series were edited into this theatrical feature film. Taken together, the two episodes ran 148 minutes, without commercials, while the film runs 125 minutes.