In the future, humans have been forced to evacuate Earth after it becomes uninhabitable; they settle on a new planet called Nova Prime. The United Ranger Corps, led by famed General Cypher Raige, defends the new human settlement against alien creatures known as Ursa, which track humans through the pheromones released when they are afraid. Cypher's estranged teenage son, Kitai Raige, is a cadet in the Ranger Corps who endeavors to gain his father's respect and live up to his legacy. Kitai blames himself for the death of his sister, whom an Ursa killed, and feels the weight of his father's disappointment despite his aspirations to become a Ranger.

Cypher decides to take Kitai on a mission to a training outpost as a bonding experience, hoping to mend their strained relationship. However, their spacecraft encounters an asteroid storm and is forced to crash-land on the now-quarantine Earth. The crash is catastrophic, killing all onboard except for Cypher and Kitai. With Cypher critically injured, Kitai must traverse the perilous, evolved terrain of Earth to retrieve an emergency beacon located in the tail of the ship, which landed some distance away. Earth's environment has dramatically changed; it's filled with evolved animal and plant life that has become hostile to humans. To survive, Kitai must overcome his fears and evolve, as his father guides him through the journey, relying on Kitai's resolve to face the dangers of the reborn Earth and signal for rescue.