In deep space, two astronauts, Corporal Bower and Lieutenant Payton, awaken in a hyper-sleep chamber aboard a seemingly abandoned spaceship. Disoriented and suffering from memory loss, they struggle to piece together the mission and the ship's purpose. As they venture into the eerily silent corridors, they discover that the vessel, meant to transport 60,000 passengers to a distant planet, harbors more secrets than they anticipated. Devoid of its crew and with systems in disarray, the ship's dark and maze-like interior covers hints of a mysterious catastrophe and an escalating sense of dread.

Bower sets off to explore the ship for clues, while Payton remains in the control room to provide guidance. Encountering fellow survivors, Bower realizes that they are not alone; aggressive, mutated creatures lurk in the shadows, hunting them. As the survivors work together to fend off the monsters and unravel the truth behind their mission, they face the psychological threat of "Pandorum," a severe space travel-induced psychosis that can drive them to paranoia and madness. With the clock ticking and danger closing in, their fight for survival becomes increasingly desperate.