When playing as the Colonial Marine, the player begins at a research station on LV-426 built to study the derelict spacecraft where the "Nostromo" crew first encountered the Alien eggs in the film "Alien" (1979). Aliens attack and the player must fight their way through the research facility, the derelict ship, and an adjoining colony. Next the player explores the atmosphere processing station and shuts down its cooling valves in order to cause an explosion which will wipe out the Aliens. The player character escapes in a drop ship and travels to Odobenus Station in orbit above the planetoid, where they battle more Aliens, Predators, facehuggers, and cybernetically-enhanced Aliens until reaching the spaceship "Tyrargo". Aboard the ship the player battles more enemies including an Alien/Predator hybrid and "praetorian" Aliens. The player then battles an Alien queen, defeating it by expelling it through the airlock.