In 2379, two hundred years after the events of Alien 3, military scientists on the space vessel USM Auriga create a clone of Ellen Ripley, designated Ripley 8, using DNA from blood samples taken before her death. The xenomorph queen's DNA has been mixed in with Ripley's, so the clone grows up with an embryo inside it. The scientists extract the embryo, raise it, and collect its eggs while keeping Ripley 8 alive for further study. As a result of the xenomorphs' DNA inside her, the clone has enhanced strength and reflexes, somewhat acidic blood, and a psychic link with the xenomorphs. Additionally, the xenomorph's genetic memory allows the clone to have some of Ripley's memories.
A group of mercenaries comprising Elgyn, Johner, Christie, Vriess, Hillard and Call, arrives at Auriga on their ship Betty. They deliver several kidnapped humans in stasis. The military scientists use the humans as hosts for the aliens, raising several adult xenomorphs for study.