The Butterfly Effect is a 2004 American psychological thriller film directed and written by Eric Bress and J. Mackye Gruber. The film stars Ashton Kutcher, Amy Smart, Eric Stoltz and others, and was distributed by New Line Cinema. The title is a reference to the butterfly effect, which theorizes that a change in something seemingly innocuous, such as a flap of a butterfly’s wings, may have unexpected larger consequences in the future, such as the path a hurricane will travel.
The film was followed by two largely unrelated direct-to-DVD sequels, The Butterfly Effect 2 and The Butterfly Effect 3: Revelations.
Evan Treborn (Ashton Kutcher), who suffered severe traumas as a boy (Logan Lerman) and a teenager (John Patrick Amedori), blacks out frequently, often at moments of high stress. While in therapy, he finds that when he reads from his adolescent journals, he travels back in time, and is able to essentially “redo” parts of his past, thereby causing the blackouts he experienced as a child. There are consequences to his choices, however, that he then propagates back to the present: his alternate futures vary from frat boy to prisoner to amputee. His efforts are driven by the desire to undo the most traumatic events of his childhood which coincide with his blackouts, including saving his childhood sweetheart Kayleigh (Amy Smart), from being molested by her father (Eric Stoltz) and tormented by her sociopathic brother (William Lee Scott).
The actions he takes, and those he enables others to take during his blackouts, change the timeline in the new future wherein he awakes. As he continues to do this, he realizes that even though his intentions are good, the actions he takes have unintended consequences. Moreover, the assimilation of dozens of years’ worth of new memories from the various alternate timelines he has caused, are causing him brain damage. Ultimately he decides that his attempts to alter the past end up only harming those he cares about. He travels back in time once more to the first day he met Kayleigh and scares her away. He succeeds in undoing his childhood as he knew it, and then destroys all his journals so that he’s not tempted to bring any of it back.
The film ends eight years in the future with Evan leaving an office building and passing Kayleigh on the street. After a moment’s hesitation, he lets her pass by without noticing him.
 Alternative endings
The director’s cut of the film ends with Evan deciding that his ability to alter the past is causing tremendous harm. He travels back to the day of his birth, and as a fetus, strangles himself with his umbilical cord. His mother’s screams of “Not again!” suggest that the fetuses of the miscarriages before him had the same abilities and ultimately chose the same path he did. The resulting time-line shows his friends and family happier without him. A voice-over replays his mother’s confession (originally heard when visiting the fortune teller earlier, saying that he was the third of three brothers, the other two having died during birth), this time altered to her telling her fourth child, now a daughter, that she survived while her three children before her did not. This, along with the still-birth of the three boys, implies that this form of the time-traveling gene (TBE3: Revelations, uses a different form) is only active in the male side of the lineage, though it is unclear if a female can pass it on. Beside that, the Director’s Cut includes numerous additional changes/extensions compared to the theatrical version.
Another alternative ending shows Evan and Kayleigh stopping on the street when they cross each other. They introduce themselves and Evan asks her out for coffee.
Yet another ending is similar to the one shown in the film, except this time Evan, after hesitating, turns back and starts following Kayleigh.