Carter Nix (John Lithgow) is a respected psychologist, loving husband and devoted father who decides to take a year off to help raise his daughter. Carter's wife Jenny (Lolita Davidovic) is pleased to have her attentive husband home: at first.

When Carter shows obsessive behaviour toward their daughter, Jenny becomes concerned, and to complicate matters, Jenny's old flame re-enters her life. But nothing can prepare her for the emergence of Carter's multiple personalities, and a fiendish plot to recreate the infamous experiments of his deranged father.