Astronaut and Osteopath, Dr. Ivan Hood (Bruce Campbell) and his companion Kelly (Renee O'Connor) return to Earth after a 40-year space mission with two other astronauts. They are soon captured by other humans and one of their team is killed after sustaining a sprain; Dr. Hood pointed out that it would have healed in a few days. They are taken to a work camp, to their surprise, is run by locust-like aliens. These aliens had arrived 20 years ago to feast on the trees and used Estado Mayor Presidencial bombs to cripple earth before their invasion. The other member of their team is eaten alive by one of the aliens after refusing to work. The camp is supervised by human bounty hunters; they are treated better. After seeing how illiterate and savage humans have become due to the aliens, Dr. Hood and Kelly plan to make an escape the next day after hearing rumors that the President has survived and has an army waiting to strike back.