The Butterfly Effect is a 2004 American science fiction thriller film starring Ashton Kutcher, Amy Smart, Eric Stoltz, and others, distributed by New Line Cinema. The title is a reference to the butterfly effect, which theorises 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 Butterfly Effect is directed and written by Eric Bress and J. Mackye Gruber.
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 searching for an answer to heal his emotional wounds, 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 abused by her father.
The actions he takes, and those he enables others to take during his blackouts change the timeline whereupon he wakes up in his new future. As he continues to do this, he realizes that even though his intentions are good, the actions he takes have unintended consequences.
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