By March 14, 2077, Jack Harper and Victoria “Vika” Olsen are among the few humans left on Earth. Sixty years earlier, a race of alien scavengers destroyed the Moon and invaded Earth; humanity won the war, but nuclear weapons and the loss of the Moon left most of the planet uninhabitable. With Vika as his communications officer, Jack serves as “Tech 49”, repairing the combat drones that hunt the remaining scavengers and guard the “hydrorig” generators converting seawater into fusion energy. Led by mission director Sally from aboard the “Tet” space station orbiting Earth, they will soon leave for humanity's new home on Titan. Although their memories have been wiped, Jack has recurring dreams of a life before the war with an unknown woman.
Exploring the ruins of the New York Public Library, Jack narrowly escapes a scavenger ambush. After a hydrorig is destroyed, he discovers the scavengers are using the Empire State Building's antenna to transmit coordinates to outer space. After disabling the transmitter, he visits his secret cabin filled with mementos from Earth's past. An unknown object crash-lands at the transmitted coordinates; in the wreckage, Jack finds five humans in stasis chambers, including the woman from his dreams. Drones kill the hibernating humans, but Jack protects the woman and brings her to his base. He and Vika revive the woman and learn her name is Julia, realizing she was in stasis aboard her ship Odyssey since before the war.
Jack and Julia return to the crash site and recover Odyssey's flight recorder, but are captured by scavengers and taken to Raven Rock Mountain Complex. Their leader, Malcolm Beech, reveals that the scavengers are humans, disguised to stay hidden from the drones. Another drone attacks, and Beech releases Jack and Julia to discover the truth in the “radiation zone”. Julia reveals she is Jack’s wife, triggering his memories of proposing to her at the Empire State Building.
Vika sends a craft to retrieve Jack and Julia, but is heartbroken to see them reunited. She alerts Sally, who activates a drone that kills Vika before Julia destroys it. Jack and Julia escape in his craft and destroy the drones pursuing them, but are forced to eject over the radiation zone. Another technician, "Tech 52" – revealed to be a clone of Jack – arrives to repair the drones. Jack incapacitates him, but Julia is shot, and Jack flies to his clone's base for medical supplies, tricking a clone of Vika into believing he is "her" version of Jack. He takes Julia to his cabin, where she recuperates and they re-consummate their marriage.
They return to the scavenger base, and Beech explains that the Tet is an alien artificial intelligence: determined to acquire Earth's resources and wipe out humanity, it destroyed the Moon and invaded Earth with an army of drones and Jack’s clones; humanity’s victory and escape to Titan is a Tet fiction. Jack reprograms a captured drone to sabotage the Tet, but more drones attack the base, leaving Beech gravely injured and the captured drone damaged beyond repair.
Jack volunteers to deliver Julia to the Tet, allowing him to infiltrate the space station and detonate Odyssey's nuclear fuel cells. En route, Jack learns the truth from Odyssey's flight recorder: he was the commander of a NASA mission to explore Titan, with Vika as his co-pilot, Julia as a crew member, and Sally as their mission director on Earth. After their ship Odyssey was diverted to investigate the Tet, Jack jettisoned the sleep module, allowing Julia and the hibernating crew to eventually return to Earth, while he and Vika were captured and cloned.
In the present, Jack enters the Tet, finding thousands of clones of himself and Vika in stasis. Confronted by the Tet’s projection of “Sally”, Jack opens the stasis chamber to reveal Beech; Julia was sent safely to the cabin instead. Jack and Beech detonate their bomb, sacrificing themselves to destroy the Tet. Three years later, Julia has given birth to her and Jack’s young daughter. They meet the surviving resistance members, accompanied by Tech 52, who has regained Jack’s true memories.
Tom Cruise as Jack Harper
Morgan Freeman as Malcolm Beech
Olga Kurylenko as Julia Rusakova Harper
Andrea Riseborough as Victoria "Vika" Olsen
Nikolaj Coster-Waldau as Sergeant Sykes
Melissa Leo as the Tet/'Sally
Zoë Bell as Kara