Anna finds a picture she had taken of the "Jane" she met and shows it to Ethan. He breaks down and tells her the truth: Jane and Alistair are his adoptive parents, and Katie, the woman Anna assumed was Jane, is his biological mother. Katie tracked the family down in order to see her son again, but her frequent unwanted visits led to an altercation with Jane, which resulted in Katie being stabbed. Alistair and Jane hid the body and lied to the police.
Anna urges Ethan to talk to the police, but he convinces her that he will talk his parents into turning themselves in. Ethan later sends a text confirming he and his parents are going to the police. That night, Anna realizes that Ethan mentioned something that he couldn't have known. She is startled by Ethan in her room, where he confesses that he has psychopathic tendencies, that he has been sneaking into her home at night to watch her, and that he has stalked other women as well. He reveals that he was the one who killed Katie because of his resentment about the abuse and neglect he faced as a child under her care, and that his father knew, but kept it a secret to protect Jane.
Realizing that he intends to kill her too, Anna flees. He pursues her to the roof where she pushes him through an old skylight to his death. Alistair is arrested as an accessory to Katie's murder, and Anna slowly starts her life over again.