Telly Paretta (Julianne Moore) believes that her son Sam (Christopher Kovaleski) died 14 months ago in a plane crash, but her husband Jim (Anthony Edwards) tells her that she's delusional and that they have never had a son. Her friend Eliot (Jessica Hecht) doesn't appear to believe in Sam's existence despite her closeness to him. Dr. Munce (Gary Sinise) tells her that Sam was merely a figment of her imagination and that she is just imagining a life that might have been. He recommends that she be sent to a hospital, but she runs away and meets with a man named Ash (Dominic West), who she thinks is the father of a girl named Lauren (Kathryn Faughnan), who was Sam's friend and died in the same crash. At first he dismisses her, claiming he never had a daughter, and calls the police. After she is taken into custody, he remembers his daughter and rescues Telly. Together they escape and go into hiding, pursued by National Security agents.