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.

Nellie is divorced by wealthy Jack Givens because after a miscarriage even in vitro fails to overcome her infertility. She finds herself destitute as her own accounts were plundered by someone who stole her maiden identity, Eleanor Kendall. Bank officer Dave, an old friend and potential lover, helps her trace the impostor to Montréal and prevent the imposter's purchase of a Corsica home. Nellie starts an affair with British doctor Christopher Dolan, who is in town for a conference, and bumps into Eleanor, a local French tutor and single mother. Instead of informing the police, she gets acquainted with and comes to like 'Eleanor'. Finally the truth catches up, but proves more complex and perilous than anyone anticipated.