Two hundred years after the events of Alien³, Lieutenant Ellen Ripley is cloned by military scientists interested in the Alien Queen she had become a host for. Like the "Company" from the earlier films, the military intends to use the Queen to breed a force of bio-weapons. But then something goes wrong; the Aliens they are studying manage to escape, and swarm throughout the science ship. It's up to four stranded heroes - Ripley, Call, DiStephano and Christie - to wipe out the Aliens, and return the ship safely to Earth.