Theo Conroy (Kevin Bacon) is a middle aged, recently retired banker who is married to Susanna (Amanda Seyfried), a young actress, with whom he has a young daughter named Ella (Avery Essex). He suffers from nightmares. One day, when Theo tries to visit Susanna on set, he is annoyed when he is denied access onto the set. Theo is further displeased upon realizing that Susanna is filming a sex scene. There is mention of Theo being recognized and unliked.The Conroys decide to get away and book a vacation home in Wales before Susanna goes to work in London. Theo and Susanna marvel at the spaciousness of the home, but there is something unusual about the house. Theo has trouble figuring out the light switches, time passes unusually fast, and both he and Susanna have nightmares. One night, as Ella makes shadow puppets in her room, she sees what looks like the shadow of a man appear on the wall.Susanna and Ella go for a walk the next morning, and Ella asks her mother why people hate Theo. Susanna reluctantly explains that Theo's first wife drowned in the bathtub, and people suspected that Theo killed her, although he was found not guilty after a high-profile trial.Theo goes into town for groceries while the girls are out. The shopkeeper asks Theo if he is staying up in that house and asks if he's met Stetler, the supposed owner. Theo explains that they booked the house online and haven't met the owner. The shopkeeper tells him there have been many houses on that hill. He is given a ruler and told to measure the right angles, which leaves Theo confused. When Theo leaves, he's approached by a local woman who also asks if he's staying in the house and if he's met Stetler.When Theo returns home, he finds out that Susanna told Ella about his ex-wife's death and admonishes her for it since he was waiting for the right time to talk to her about it himself.Later, after dinner, Theo snoops around on Susanna's devices while she is in the bath and finds nothing. He ends up apologizing for the earlier argument.Theo wanders through the house and finds what appears to be a hidden stairway in the bookshelf. He follows it downstairs and comes across what appears to be Ella's body. He knows it's a dream and tries to wake himself up by cutting his wrist and throat. Theo wakes up unharmed.The next day, as Theo watches Susanna and Ella play outside, he tries to text Susanna. As he watches her looking at her phone, he finds an identical phone on the kitchen counter with his messages on the screen. He then goes to look at his journal, which has written inside it "You should leave. Go now." He goes outside to confront Susanna about having a second phone. This leads to another argument in which Susanna admits to an affair with another actor named Max. Theo asks her to leave for the night.Theo returns to his journal to see that someone has written "You should have left. Now it's too late." He and Ella start to notice strange things about the house. They begin to measure, using the ruler he was given, and discover the kitchen is larger inside than outside. They're both confused. Ella runs inside to get her coat, but disappears when she walks back out the door. Theo thinks she's playing and goes to look for her. The two of them appear to be experiencing separate visions in the dream world, but Theo manages to get back to Ella. They agree not to leave one another alone in the house. Theo tries calling for a taxi and gets the shopkeeper to answer him, telling him that no taxis are in that area and that the devil is collecting souls from that house.Theo and Ella prepare to leave by walking into town. They see a figure standing in the window observing them as they walk away from the house. After walking in the cold for some time, they find that they have walked right back to the house. Seeing no other option, Theo convinces Ella to stay there for the night, but as they sleep, Theo enters the dream world again and sees his and Susanna's past selves as they first came to the house and admired it. He then finds that Ella is trapped and he cannot find her. He meets Stetler, who takes Theo's form to taunt him. He says he will return Ella on the condition that Theo does "what he must." Ella is returned to him, and he embraces her.Susanna returns, and Theo puts Ella in the car. He finally comes clean to Susanna about what happened with his first wife. He didn't directly kill her, but he watched as she lost consciousness because he had been angry with her for so long. Instead of leaving the marriage, he chose to watch her die. He accepts that he belongs in the house. Susanna is horrified. Theo's soul is then seen trapped inside the house, having tried to warn himself by writing the messages in his journal.The shopkeeper's voice says that some people don't leave the house, and "the place finds them." A listing for the house becomes available on a website similar to the one Theo and Susanna booked their stay on.