After collapsing, disoriented, in a Los Angeles diner, Louise (Joan Crawford) recounts the events of her life to a psychiatrist. While working as a nurse for the wife of wealthy Dean Graham (Raymond Massey), she falls in love with the Grahams' neighbor, David (Van Heflin), who rejects her affection. Following the death of Dean's wife, Louise becomes the new Mrs. Graham, but her dangerous fixation on David continues. She grows increasingly unstable as her obsession leads to madness and violence.