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.

Three detectives in the corrupt and brutal L.A. police force of the 1950s use differing methods to uncover a conspiracy behind the shotgun slayings of the patrons at an all-night diner.