After witnessing the murder of her mother 20 years ago, Alexa returns to Los Angeles seeking revenge on the man who killed her. She finds that her best way to reach this man is trough his son, who turn out to be nothing like his father.

Jimmy is a committed child psychologist who uses his own playbook, but when he is brought in to work with Ellie, he is completely unprepared for his subject—a 9-year-old psychopathic genius with nothing to lose. As he begins to understand the extent of her capabilities and the fate that has been planned for her, he struggles to overcome her defenses before it is too late for them both.