The very fact that the film “runs backward” allows also an inverse reading
of his intentions and goals. Considered as a productive pathology, Leonard’s amnesia would remind one of the importance of forgetting, rather than remembering. [Here,] revenge becomes a meaningless concept.
— Thomas Elsaesser: The Mind-Game Film
Leonard Shelby is tracking down the man who raped and murdered his wife. The difficulty of locating his wife's killer, however, is compounded by the fact that he suffers from a rare, untreatable form of short-term memory loss. Although he can recall details of life before his accident, Leonard cannot remember what happened fifteen minutes ago, where he's going, or why.