In a dystopian 2050, fighter pilot Adam Reed steals a time jet to escape to 2018 to save his wife, Laura Shane. In the process, he gets injured and crash-lands in 2022. The story then shifts to 12-year-old Adam in 2022, whose father Louis died a year previously. He is bullied at school, gets suspended for fighting in school, and is distant from his mother Ellie. When he is home alone one night, he finds the injured future Adam. The younger Adam refuses to trust the stranger, but future Adam inadvertently mentions the names of both the younger Adam and his dog, Hawking. The younger Adam soon realizes that the stranger in front of him is his future self.

Due to a safety feature preventing him from flying because of his injuries, Adam must bring along the younger Adam and use his DNA to enter his jet. They both are soon attacked by Maya Sorian, the leader of the dystopian world, and her assistant Christos, but are saved by Laura, who had faked her death and stayed off-grid in an unknown location. After surviving the attack and comparing notes, Laura and the Adams realize that after the invention of time travel by Louis Reed and his subsequent death, Sorian had monopolized the discovery. During her visit to 2018, Laura learned Sorian frequently came and advised her past self in order to secure her future wealth and power. To protect her secret, Sorian ordered Laura's death. Although Laura survived the assassination attempt, destruction of her time jet left her stranded in the past. The sudden arrival of Sorian's goons interrupts the reunion, and Laura fights off the attack long enough for the two Adams to escape to 2018.

In 2018, the Adams meet Louis Reed in an attempt to enlist his help, but their father refuses any assistance out of concern for the effect on the time stream. That night, Sorian meets and warns her past self about Adam. Meanwhile, the Adams share their common feelings about their father in a motel. The next day, they both set off to destroy the time travel machine. On arrival at Sorian Technologies, they are attacked by Sorian's soldiers, but are unexpectedly saved by Louis, who has changed his mind and agrees to guide them. Louis reveals that destroying the machine will not destroy time travel as long as Sorian has his algorithm with all the math and constraints to control the process. Meanwhile, 2050 Sorian captures the younger Adam.