Players take the role of Wesley Tyler, a senior mechanic on the IGTO Repair Base on Ganymede, who is tasked with the repair of various systems. At the start of the game, Tyler is ordered to repair the backup generators, and he and two other technicians drive out to fix them. On the way there, they discuss Tyler's past, how he was previously in charge of a security team, before being blamed for an accident involving faulty equipment. Upon fixing the power however, Tyler loses radio contact with the others, and starts encountering small three-legged insect like creatures. He then starts finding bodies, and larger more dangerous versions of the aliens he had encountered before. He finds a pistol and begins to battle the increasingly hostile aliens.