Dr. Carter Nix is a respected child psychologist who takes a year off from his practice to help raise his daughter, Amy. His wife, Jenny, starts noticing odd behavior from Carter, who seems overly attentive and protective of their daughter. As Jenny grows concerned, it becomes clear that Carter has a darker side, manifesting through his multiple personalities, including his sinister alter ego, Cain. Cain is involved in a series of disturbing activities, hinting at a deeper, more malevolent plan involving children.

Jenny, troubled by Carter's behavior and her own extramarital affair with ex-lover Jack Dante, discovers shocking truths about her husband’s psychological state. Unable to ignore the mounting evidence, she becomes determined to uncover the extent of Carter's actions and protect her daughter. The psychological tension escalates as the different facets of Carter's personality struggle for dominance, leading to a compelling and suspenseful narrative filled with unexpected twists and turns.