Intergalactic extremist Alex Windham (Bruce Campbell) has seized control of Dome 4, a scientific outpost on another planet, after escaping from a penal colony on Mars. Windham is forcing the staff of Dome 4 to construct new weapons that he can use to destroy his enemies, but he doesn't know that one of his captives is the wife of interstellar lawman Chase Moran (Joseph Culp) — and Moran will allow no harm to come to his wife.