As a Marine, the game starts out above the planet, with the Marines squads on two separate ships, one of which is identified as the USS Marlow. The Marines have been given orders for a combat drop. When the Predators’ ship comes out of cloak and destroys the Marlow, Major Van Zandt directs the surviving shuttle to land. The player Marine, dubbed “Rookie”, is knocked out during the drop, and regains consciousness in the heart of the chaos itself. At Corporal Tequila’s direction, Rookie is sent into several parts of the wrecked human colony with the purpose of getting systems back online and locating all the surviving Marines, especially Major Van Zandt. However, the Major is discovered cocooned, forcing Rookie to shoot him.
As an Alien, the game begins in a laboratory, where two humans are being kept imprisoned. As one of them wakes up, a chestburster emerges from the other, killing him. Soon after, a chestbuster breaks through the other’s body, killing him as well. As scientists enter the room to collect the specimens, they find that “Specimen 6” is missing. The missing chestburster then emerges from the second victim’s mouth, rather than the containment tube, and, as a result, the room is gassed by head scientist Dr. Groves, killing the two other scientists and subduing the chestburster; however, Mr. Weyland prevents the death of the creature, impressed with the chestburster’s cunning, and tells Groves to assign the creature to a special program, the alien code-named ‘Specimen 6’.
As a Predator, the game starts in the jungles, where a youngblood is proving himself strong and fit enough for the rank of Elite. Once the trials are complete, the Elite, named “Dark”, is dispatched with a group of other Predators to a planet in order to investigate a distress call, sent by a youngblood hunting party on another planet (BG 386). On arriving at BG 386, the Predators destroy the orbiting Marine ship, the USS Marlow, and launch the Elites onto the planet’s surface.