This sci-fi/horror sequel is set in the 21st century where the human race has been decimated by a man-made plague. Most of the normal survivors now live underground while the Earth's surface is populated by terrifying mutants. The survivors have developed a plague vaccine, but must gather the ingredients upon the dangerous surface. This version opens at the Rocky Mountain Lab, where they have run out of the vaccine and people are getting sick. A few days earlier they sent David Pennington topside to gather more ingredients. Unfortunately he has disappeared. The lead scientist then sends out three people to find David, but instead they end up tangling with a mutant. One of their party is killed. During the scuffle, they manage to cut off one of the creature's fingers and bring it back for research. Meanwhile, David wanders the desert world and meets the beautiful, pregnant Ariel, with whom he falls in love. Just before making it down to safety, the two are attacked by the mutants and one of them rapes her. When she eventually gives birth, her baby is terribly deformed. Meanwhile the finger regenerates into a new mutant horror and now with two of the dreadful creatures to deal with, things look bleak.