In The Butterfly Effect Evan Treborn (Ashton Kutcher) has lost crucial moments of his life, his childhood scarred by a series of terrifying events he can't remember. When Evan realises that by reading his diaries he can unlock the past and go back in time, he tries to reclaim the missing memories by tampering with the past... with unexpected and distastrous results!
The more Evan tampers with time, the more his life, and those of his friend Kayleigh (Amy Smart) begin to unravel, and he discovers there is no such thing as a happy ending!