Plot
Growing up, Evan Treborn, his friends Lenny Kagan and Kayleigh Miller, and her brother Tommy suffered many severe psychological traumas that caused Evan to experience frequent amnesia. These traumas include being forced to create child pornography with Kayleigh by Tommy's father, George; Evan nearly being strangled to death by his institutionalized father Jason, before Jason is killed in front of him by guards; accidentally killing a mother and her infant daughter while playing with dynamite; and Tommy burning Evan's dog Crockett alive. Evan keeps meticulous journals of his day-to-day life as a coping mechanism.
Some time later, while entertaining a girl in his college dorm room, Evan discovers that he can time-travel and redo parts of his past by reading his journals. His time-traveling episodes account for the frequent blackouts he experienced, since those are the moments when his older self occupied his consciousness.
After a traumatized Kayleigh commits suicide, Evan travels back in time and prevents George from molesting her. He comes back to a reality where he and Kayleigh are a happy couple in college, but he discovers George ended up taking out all of his abusive tendencies on Tommy, who grew up to become even more violent and dangerous. When Evan is attacked by Tommy, he kills Tommy in self-defense and is imprisoned. There, he manages to time-travel once more after his mother brings him a journal during a visit.
Upon returning, Evan stops Tommy from killing Crockett, but Lenny, relentlessly bullied by Tommy and mentally unstable following the dynamite incident, kills Tommy with a metal shard. Following Tommy's death, Evan wakes up in a new reality where Lenny has been institutionalized, and Kayleigh is a drug-addicted prostitute. Evan travels back to prevent the dynamite accident; while Tommy shields the mother and baby from the blast, Evan is caught directly in the explosion.
In the new reality, Lenny and Kayleigh are happily in a relationship, and Tommy has become religious, but Evan is a double amputee. His mother, stricken with grief over her son's injuries, began smoking obsessively and developed lung cancer. To save his mother and himself from this fate, Evan goes back to his childhood and prepares to discard the lit dynamite, but Kayleigh picks it up when it is smacked out of his hand by her father, and it explodes, killing her.
Evan awakens in a mental hospital and finds that his journals no longer exist, and he has suffered irreversible brain damage due to the rigors of time travel. He discovers that his father had the same ability before losing the photographs that allowed him to time-travel. Evan ultimately reasons that he and his friends will never have good futures as long as he keeps altering the past.
After escaping the hospital staff and barricading himself in an office, Evan uses an old home movie to travel back to the day he first met Kayleigh. He intentionally upsets her so that she and Tommy choose to live with their mother rather than their father in the wake of their parents' divorce. As a result, the siblings are spared a destructive upbringing, and Lenny is never bullied and the dynamite incident never happens.
Evan awakens in a college dorm room, where Lenny is his roommate. To ensure that his plan worked, he asks where Kayleigh is; Lenny does not know who Evan is referring to. Satisfied that his friends' futures are secure, Evan burns his journals and videos to avoid altering the past ever again.
Eight years later, in New York City, Evan and Kayleigh pass each other on the street, briefly look at each other, and continue walking.
