Amityville, Long Island, New York, 1975Ed and Lorraine Warren (Patrick Wilson and Vera Farmiga) are sitting with the Lutz family in the infamous Amityville home. A year earlier, Ronald DeFeo, Jr. murdered his family with a shotgun, and the Lutz family claims to have been experiencing paranormal phenomena. The Warrens conduct a seance, in which Lorraine has a vision where she sees herself in Ronald's position on the night of the murders. She watches herself committing the acts, first with Ronald's parents, and then his three siblings. Lorraine then encounters a demonic creature taking the form of a nun, followed by a man dying. Lorraine screams, and Ed pulls her out of the vision and comforts her.Three years later in Enfield, England. Janet Hodgson (Madison Wolfe) is sitting outside the school with her friend Camilla (Emily Tasker) as Camilla smokes a cigarette. She passes it to Janet right before a teacher walks outside and scolds the girls for smoking. She confiscates the cigarette and takes a puff.Janet lives with her older sister Margaret (Lauren Esposito), younger brothers Johnny (Patrick McAuley) and Billy (Benjamin Haigh), and their mother Peggy (Frances O'Connor). The Hodgsons are struggling financially, the children's father left them for a neighbor woman, and Billy has a speech impediment that gets him bullied at school. Peggy has self-doubts as a single parent.At night, Janet and Margaret are sleeping in their room, when Janet begins to feel a disturbing presence. It sounds as though she's speaking to herself, but then she begins responding with a growling, raspy voice that claims "This is my house!" Margaret thinks Janet is fooling around, until she stands by Margaret's bed, and the voice of an older man behind Margaret repeating the statement. Margaret turns the light on and finds nobody behind her. She decides to sleep with the light on.Back in the States, the Warrens are on a talk show to discuss the Amityville case. The other guest on the show dismisses the case as a hoax before criticizing Lorraine's supposed clairvoyance. This enrages Ed, leading to him arguing with the other man. Lorraine calms him down backstage.Janet and Billy play with a turntable based on the tune of "There Was a Crooked Man". As the children go to bed, Janet ties her arm to the bed. She ends up on the floor of the living room with no idea as to how she got down there. Billy walks around the house, when he sees a toy firetruck on the floor. He rolls it into a tent in the hallway, but moments later, the truck rolls into Billy's room. He goes back outside and rolls it into the tent, at which point a booming groan is heard. Billy runs to his mother's room while Margaret hears a pounding at her door. She opens it and sees no one outside until Janet returns, denying that she was pounding on the door.The next day, Janet is watching TV, and the channels start changing on their own. The remote has also vanished. Janet goes looking for it and finds it on the chair behind her. A ghostly figure emerges from the corner and growls, "MY HOUSE!" Janet runs back to the couch screaming.That evening, Janet ends up on the floor of her room as though she was thrown. She tells Margaret that there is someone in the house. Before Margaret can dismiss that, their beds start shaking. They scream and run to Peggy's room. She goes to the girls' room and thinks they're playing around, until the girls' dresser is shoved hard against their door.The Hodgsons head over across the street to the home of their neighbors, the Nottinghams. Peggy calls the police to inspect her house. The police find nothing, but they then see a chair sliding across the room on its own, leaving them spooked.At the Warren house, Ed is painting a picture of something he claims to have seen in a dream. It's the same demonic nun that Lorraine saw in her vision. Later, while she sits in the living room with their daughter Judy (Sterling Jerins), a noise is heard in the hallway. Judy goes outside to look. Lorraine finds her staring in horror at the demon nun. Lorraine follows it into the office. She thinks she sees the nun in the darkness, but it's just the painting. However, the demon is still in the room, and it walks up to the painting and makes it come to life. It growls as it runs toward Lorraine, causing her to see the same vision as before, only this time, we see the man who dies - it's Ed, simply saying, "I'm sorry, Lorraine" before a large wooden spike impales him. Lorraine starts screaming and scribbling into her bible before Judy snaps her out of it.People in Enfield become aware of the Hodgson's haunting. Several paranormal researchers get involved, including Maurice Grosse (Simon McBurney) and Anita Gregory (Franka Potente), the latter claiming there is a lack of evidence to suggest the phenomena is truly paranormal. Maurice and a news crew gather in the Hodgson home to interview Janet and Margaret. During the interview, Janet looks uncomfortable, and she begins to speak with the voice of a raspy old man. The entity says its name is Bill Wilkins, who is 72 years old, and demands that everyone leave his home.At the Nottingham home, the children sleep in the living room. While everyone else is asleep, Billy walks through the house and encounters a creature that takes the form of The Crooked Man, reciting the nursery rhyme monstrously and chasing Billy. When he runs to tell his mom and the others, Janet emerges with the creepy voice saying the rhyme. She then lets out a horrifying sound that shatters the glass in the room. She passes out and starts foaming at the mouth.A priest goes to the Warren home and plays an audio recording of the interview for Ed and Lorraine to listen to. The priest asks them to help in this case. Lorraine is hesitant as she explains to Ed the vision she saw of his death. He thinks it's a sign that maybe she is meant to prevent it. They decide to head over to England.The Warrens arrive in Enfield and meet the Hodgsons. Peggy shows Ed the bedroom that is now trashed, and the walls are covered in crosses. They proceed to lock the room with a chain. Lorraine meets Janet outside her house, sitting on the swingset. Janet expresses her sadness that people are avoiding her over the supposed haunting. Lorraine comforts her in saying that maybe one person can help change things, like Ed has for her. Janet says the voice she hears says it wants to hurt Lorraine.The Warrens, along with Maurice and other crew members, gather in the Hodgson living room to try and communicate with the spirit. Janet sits in the chair and starts speaking with the voice of Bill Wilkins once the adults turn their backs to her. Ed pulls out his cross necklace and puts it in front of Janet's face, making Bill sound distressed. He yells something unintelligible before everything seems to calm down.The Warrens talk to the other investigators with the evidence they have. Anita is the most skeptic, thinking Janet is playing some kind of game. Ed also appears to have doubts himself.The Warrens stay with the Hodgsons for the night. Janet finds herself in the bedroom with the crosses. They all start to turn upside down before Janet is attacked by Bill's ghost. Her screams alert the adults, who rush to unlock the door to get Janet out.On another occasion, Peggy brings Ed downstairs to the basement to inspect her water problem that left the basement flooded. Peggy thinks she sees someone behind Ed, but the ghostly vision of Bill is in the water and grabs Peggy. Ed helps her break free.The children take a liking to the Warrens as they maintain their stay. After Peggy notes that her ex-husband took the music from the house, Ed buys an Elvis record for the kids to listen to. Unfortunately, the record player stopped working. Undeterred, Ed picks up a guitar and starts playing "Can't Help Falling in Love With You". He also convinces the kids to never let bullies get them down.Lorraine speaks with Maurice privately. He says they are about to be part of history. Lorraine is uncertain with his comment, but he adds that he lost his daughter years ago and has been hoping to communicate with her in some way if it were possible.On another night, the kids hear noises coming from the kitchen. Johnny decides to investigate to fight this "bully". Margaret then screams as Janet disappears. She pops up in the kitchen with a knife, and the door lock. The adults try to get into the kitchen as things are being thrown around. They find chairs and dishware broken all over the kitchen, but Johnny and Janet are nowhere to be found. They eventually do find Johnny, and Janet is stuck inside an electrical box, speaking another unintelligible message before getting pulled out.Anita shows the Warrens video evidence of Janet herself throwing things in the kitchen to give the appearance of a haunting, making it look more obvious that she was faking. Peggy sends everyone out of the house. Later, as the kids also believe Janet was faking, she tells them that "it" was going to hurt her family if she didn't do what was told of her.The Warrens board the train to head home, even as Lorraine continues to express uncertainty over how it just appeared Janet was faking when a camera was pointed at her. Ed then plays the recordings of Bill's voice, which he realizes are connected. Played together, the messages come out to "Help me! It won't let me go!" Lorraine is then pulled into another vision. She sees the real Bill Wilkins (Bob Adrian) sitting in his chair, no longer threatening. He speaks in a riddle to Lorraine before the demon nun appears behind Bill and takes him away. This leads Lorraine to realize that Bill is just a pawn, and this demon is the true threat. They rush back to the Hodgson home while trying to decipher the riddle. Ed figures that Bill meant to say they need to find the demon's name in order to have power over it.The Warrens return to find the family locked outside the house in the pouring rain. Ed tries to break in through the back. Lightning strikes the tree in front of the house, leaving a sharpened stem that Lorraine recognizes as the thing that kills Ed in her vision. She tries to figure out the demon's name before realizing she already DOES know it. She looks into her bible and sees from her scribbling that the demon's name is Valak. She rushes into the house to go after Ed.Ed is partially blinded when a pipe bursts and sprays steam in his face. He stumbles and is attacked by The Crooked Man before coming across the room where Janet is. She stands by the window as it shatters, leaving her an opening to jump onto the stem. Ed rushes to grab her, just catching her as he holds onto the curtains that are ripping. Lorraine reaches the room and tries to save Ed, but Valak emerges and holds Lorraine back. Lorraine utters the demon's name and condemns it back to Hell. Lorraine runs to save Ed and Janet in the nick of time. Janet is just fine.In the morning, everything has calmed down. Peggy and Janet thank the Warrens for helping them. A brief text is followed that states that the Enfield haunting became one of the most notorious cases in history. Peggy Hodgson continued living in the house for 40 years until she died in the same chair as Bill Wilkins.The Warrens return home. Ed takes the Crooked Man turntable and puts it in his museum (right across from Annabelle, no less). He then hears music playing from upstairs. Lorraine put on "Can't Help Falling in Love With You". The two of them then share a dance.