Based on the life of Kitty O'Neil, a young girl who overcame her deafness to become one of the top stuntwomen in Hollywood, and the holder of the women's land-speed record for driving a rocket-powered racing car.
Planet Earth is a sequel to Gene Roddenberry's Genesis II (1973) made-for-TV movie, in which a NASA scientist, Dylan Hunt, is revived from suspended animation in the post-nuclear war United States. In Planet Earth, Dylan is now a sworn member of PAX, the colony of people who revived him. Dylan and his PAX team find another colony which is ruled by women and where all men are slaves. He is captured and sold as a slave, but escapes and organizes a rebellion. Dylan once again has a profound influence in the new world that he finds himself in, in the year 2233.
Dr. Caine, the murdering dentist from the original movie, has escaped from the mental hospital where he has been since being caught. Hoping to resume a normal life, he makes his way to a quiet Midwestern town under a false name and takes on the responsibilities of the town dentist Things are starting to look up for Caine, until the day when he catches his new love in the arms of someone else. Just as in the first movie, this sends him back over the edge and into another homicidal rampage, with his unfortunate patients bearing the brunt of his hostility.
Following the death of his father, suburbanite Obie runs away from home and winds up on Chicago's South Side. After being mugged, he befriends con artist Scam. The two then embark on a Down South adventure involving gangsters, the police, and a search for Scam's father.