Set 200 years after the preceding installment, Alien 3, Ellen Ripley (Sigourney Weaver) is cloned and an Alien queen is surgically removed from her body. The United Systems Military hopes to breed Aliens to study and research on the spaceship USM Auriga, using human hosts kidnapped and delivered to them by a group of mercenaries. The Aliens escape their enclosures, while Ripley and the mercenaries attempt to escape and destroy the Auriga before it reaches its destination, Earth.