The year is 2071 AD. City leader Dr. Varno (John Hoyt) explains that Earth is unable to support life. The residents are frantically working on a spacecraft that will take them to a planet orbiting Alpha Centauri. The four time travelers, told they may not join that space voyage, are allowed to work on recreating their time portal to return to their time. Before the colony residents can lift off, the degenerate mutant humans break in and destroy the ship and encroach on the city.