 Businessman David Kenyon never told his wife Molly that he was married before, for three years, to a highly unstable woman named Deidre. Molly discovers this fact when Deidre, who has just been released from a psychiatric hospital, pays an unannounced visit to the Kenyons. Deidre is the ex-wife-from-hell. As a teenager, she murdered her own sister, who was competing for David s affections. Deidre flirts enticingly with David, impersonates a child therapist to get close to David and Molly s son Michael, and takes an apartment across the street from the Kenyons. When David won t leave Molly, Deidre tries to ruin David by accusing David of hitting her. When Deidre kidnaps Michael from school, and holds Michael hostage in a remote cabin, David and Molly set out to rescue Michael.