Memento is a movie that was written by Christopher Nolan. This is a movie with a narrative structure like no other. By presenting events in Memento backwards, Christopher Nolan allows us to get into the mind frame of Leonard, the main character. Leonard is the narrator and like him we are presented with numerous clues, some of which may mean something other than what they initially appear to be. This approach builds plenty of suspense along the way to keep the viewer engaged. Although this approach might seem impractical, you will come to an understanding of how well it works with this storyline. The purpose for Nolan's nontraditional narrative structure is to give the audience the pleasure of slowly piecing together the plot.
Leonard Shelby suffers from the rarest of conditions, Anterograde Amnesia. He can no longer form memories. He forgets things and people as soon as they have passed from his immediate consciousness. Leonard insists he does not have total amnesia. He remembers that he was an insurance investigator in San Francisco with a home and a loving wife. He remembers all that was shattered one night when two men broke into his house. He was fast asleep and he didn't hear them, but his wife did. When she went to investigate, they raped and murdered her. It was at this point that Leonard woke up and rushed to discover what was happening. In Leonard's attempt to save his wife, he kills one of the intruders. During this vicious attack, the other intruder pushed Leonard's face against a mirror, shattering both it and Leonard's memory. Leonard has vowed to find and kill the man who took away his life. Revenge is his sole purpose in life.
Memento turns Leonard Shelby into a surrogate for the viewer, its backward narrative logic forcing us to embark on the kind of investigative work Leonard is engaged in. In most mysteries, you're dying to know what happens next. In this one, you can hardly wait for the beginning.