After
human overpopulation depletes Earth's resources, humanity builds an
interstellar ark, the
Elysium. It carries 60,000 people on a 123-year trip to colonize Tanis, an
Earth-like planet. The passengers are placed in
hypersleep, and a rotating crew wake biennially to maintain the ship. Eight years into the mission, the ship receives a transmission from Earth: "You're all that's left of us. Good luck, God bless, and Godspeed." An indeterminate time later, two members of the flight crew, Corporal Bower and Lieutenant Payton, awaken. Improper emergence from the hibernatory state leaves them both with partial
amnesia and possibly suffering from pandorum, a space-related disorder that causes psychosis when under emotional duress. The ship experiences power surges caused by an unstable nuclear reactor, and they are unable to enter the
bridge. While Payton stays behind to access the ship's computer, Bower uses the ventilation system to search for the reactor. Bower is startled by a figure rushing past. He calls out to the figure after seeing its human shape, which he then learns to be a disemboweled body. A woman (the figure) leaps at him with a curved knife and drops him to the ground and then pulls the knife along the curve of his neck without hurting him. She says things in another language before taking his boots. The mechanic, named Shepard, wakes up, startling Bower, who then frees him. Shepard mistakes Bower for a rescue team, before dousing his body in oil to cover his scent. Shepard then tells him to escape "them". Bower tries to order Shepard to tell him what is going on, but Shepard refuses, citing there is no longer a chain of command. The noise summons a group of cannibalistic humanoids who appear to respond mostly to sound. They both flee and hide but are soon found by the creatures. Shepard is killed by the group, while Bower tries to attack them with a non-lethal weapon he found earlier, which proves ineffective. He flees and continues on and encounters an environmental scientist, Nadia, and a farmer, Manh, who does not speak English; both are hostile. He encourages them to band together, and the trio flees into a barricaded chamber, where they find a cook named Leland. Leland has been awake for years, living off the water oozing through parts of the ship, the algae it creates, and resorting to cannibalism. Payton encounters Corporal Gallo, who claims the ship is lost in space and that he killed his team in self-defense. Leland feeds Bower's group and shows them mural drawings depicting what has happened: after Earth vanished following an unknown catastrophe, Gallo went insane, killed his crew, and induced pandorum in other passengers. After goading them into a violent and tribal culture, Gallo went back into hypersleep. Aided by accelerated evolution from an enzyme meant to help colonists adjust to life on Tanis, the descendants have turned into cannibalistic mutants. Leland gasses the group, intending to eat them, but Bower convinces him the reactor must be stabilized. As they search the ship for the reactor, Bower hopes to find his wife in an area for family in hypersleep but remembers that she died with everyone else on Earth when she refused to join him. This revelation almost makes him give up and pushes him closer to insanity. After surviving an encounter with the cannibals, Bower's group finds the reactor. A crowd of mutants sleep under the reactor, and Bower crosses a walkway to reset it. The walkway collapses, and Bower climbs down into the mutant pit to reach a ladder. While Manh distracts the mutants, Bower restarts the reactor, killing many mutants. Leland flees, and Manh is cornered by the mutant leader. Manh kills the leader but is killed by a mutant child he hesitates to slay. Gallo becomes increasingly agitated, and Payton prepares a sedative. As they wrestle over the sedative, Gallo is revealed to be a hallucination as Payton
is Gallo. Gallo killed the real Payton long ago when he developed pandorum upon hearing Earth was gone. Because he went into Payton's pod, Gallo mistakenly believed himself to be Payton when he woke up with amnesia. Leland reaches the bridge, and Gallo kills him with the sedative. When Bower and Nadia confront him, Gallo opens the shutters on the bridge's windows, revealing that the ship is adrift in deep space with no stars visible. The shock pushes Bower further toward insanity. Taking advantage of Bower's mental state, Gallo argues they must maintain the violent society rather than revive civilization. Nadia observes
bioluminescent ocean life through the windows, and the computer displays that 923 years have elapsed since the mission launched. The ship reached Tanis 800 years ago and landed itself in the ocean. Bower hallucinates a mutant attack and breaks a window. As water pours into the ship, Nadia and Bower climb into a hypersleep pod and eject it. The flood triggers an emergency protocol which ejects the remaining 1,211 untainted pods to the surface, while Gallo and the remaining mutants drown. Bower and Nadia surface near a lush
coastline, and they witness the other pods ascend. ==Cast==