An ordinary woman discovers that her life was not always ordinary in this action thriller. Samantha Caine (Geena Davis) is a typical, well-mannered single mother working as a schoolteacher when she isn't looking after her children.
Nothing on the surface would seem to be remarkable about Samantha's life, but every once in a while she has vague memories and unexplained impulses that don't add up with her current life experience; she has scars but no idea of how they got there, she suddenly displays a deadly talent for knife-throwing while chopping vegetables for dinner, and when she sees a deer, she suddenly attacks it with her bare hands.
When an auto accident and a television news broadcast stirs some more uncomfortable memories, Samantha hires private investigator Mitch Hennessey (Samuel L. Jackson) to look into her past and see what he can find.
Mitch learns that Samantha isn't really Samantha after all -- her name is Charley and she used to be a professional assassin with a secret government intelligence program. After a severe head injury, Charley developed a case of amnesia, and in time she developed her new personality as Samantha.
However, her old boss has kept tabs on her, and now that it looks as if the old Charley is starting to come out again, he sends a pair of hit men after her to see to it that she doesn't remember anything else; soon Samantha and Mitch are on the run, trying to outdistance the killers as they get to the bottom of Charley's secret life.