In the year 3000, Earth is a desolate wasteland. The Psychlos, a brutal race of giant humanoid aliens, have ruled the planet for a thousand years and use human slave labor to strip its minerals (especially gold) and other resources. A few primitive hunter-gatherer tribes of humans live in freedom in remote, hidden areas, but after ten centuries of Psychlo oppression they have abandoned any hope of regaining control of their planet. Jonnie Goodboy Tyler rejects this universal hopelessness and leaves his tribe in the Rocky Mountains on a journey of exploration with a nomad hunter named Carlo. Both are captured by a Psychlo raiding party and transported to a slave camp in the ruins of Denver, the Psychlos' principal base of operations. A massive dome over the base protects the Psychlos from Earth's atmosphere, which is toxic to them.