This psychological thriller was cowritten by Steven Pressfield, who went on to become a successful novelist with The Legend of Bagger Vance (2000) and historical fiction such as Gates of Fire and Tides of War. Linda Hamilton stars as Lauren Porter, a well-regarded professor of psychology who fears that she may be suffering from multiple personality disorder. As a young girl, she received psychological scars when her mother murdered her stepfather and then committed suicide. She approaches one of her students, Tom Beckwith (James Belushi), a former cop who has quit the force in order to study psychology, and tells him of her concerns. Although he is struggling with his own relationship with his daughter, Beckwith agrees to trail Porter, and before long she has indeed slipped into a totally different personality, that of Lena, a club-hopping swinger. When Lena gets into trouble with a man she's picked up, Beckwith intervenes and receives a brutal beating. Soon, the murder of an investigator and the death of Porter's ex-husband are laid at her feet.