This is a complex story about Leonard Shelby (Guy Pearce), a man whose ability to make new memories is damaged when he is struck in the head while confronting two drug dealers who are attacking his wife at their home in the middle of the night. His wife and one of the drug dealers are killed during the attack. Leonard then devotes his life to finding and killing the second attacker. Before finally achieving his goal, he is manipulated by others who use his condition for their own purposes.
The movie alternates between color and black and white sequences. The black and white sequences proceed in chronological order, but the color sequences proceed in reverse chronological order. The forward black and white scenes and the reverse color scenes alternate until they meet in the middle of the story at the end of the film.
In the two disc DVD set, the second disc contains the movie in chronological order. To play this version of the movie: (1) select the clock icon; (2) select the answer 'C' to every multiple choice question; and (3) arrange the tire changing steps in reverse chronological order (3-4-1-2). The movie will then begin to play (with the credits first - in backward order). Some functions (fast forward, chapter skip, etc.) are disabled.
This is a synopsis of the story as presented when put together in chronological order. It is not the plot order presented in the film.
The story starts in black and white. Leonard Shelby wakes up in a room at the Discount Inn puzzled as to why he is there. The phone rings and he speaks with an unknown caller. He tells the caller that he suffers from anterograde amnesia, a condition which makes him unable to create new memories. He describes the condition by detailing the story of Sammy Jankis (Stephen Tobolowsky), who had the same problem.
Leonard describes how one must have a system of notes to deal with the problems and a drive to use them. Leonard says he has the drive that Sammy never had and the viewer sees Leonard