Psychologist Philip Clark’s (Ben Affleck) patient Daphne (Emily Alyn Lind) has lived a life of abusive relationships. To help her, Philip tries a new kind of therapy, sharing his own personal dilemmas with her to tell more. A few years earlier, Philip and his wife lost their son Evan in a tragic accident. The decision to share this with Daphne has caused some controversy among those around Philip, as many believe he is genuinely trying to get therapy for himself.
Later, after the death of her close friend, it is discovered that Daphne has also died and the police believe it to be a suicide. In turn, people in Philip’s life begin to wonder if his unorthodox therapy techniques are a cause. Philip and his family then meet Daphne’s brother, a writer named James Flagg (Sam Claflin). James quickly warms to Philip’s family and Philip even decides to buy one of his books, which will take a few weeks to arrive. James becomes particularly close with Philip’s daughter Lucy (India Eisley) and his wife Grace (Michelle Monaghan). He seduces them both and gains their trust while ruining Philip’s life in the process. James lures Grace and Lucy with a vision of a caring and understanding man unrelated to any of their existing traumas.
When he finally receives the book, Philip learns that James is someone else’s name, while the person they know is actually a man named Eric Dalton, who is Daphne’s abusive ex-boyfriend. Not only that, he’s also the one who kills Daphne’s girlfriend to make her lonely and want him. When that doesn’t work, Eric kills her. While Philip cannot save Daphne from Eric, he must now overcome the trauma that is tearing his family apart in order to save Lucy and Grace from him.
If you or someone you know is having suicidal thoughts, please call the National Suicide Prevention Lifeline at 1-800-273-TALK (8255).