In 1978, a young developmentally-challenged girl named Adelaide stands outside of a foreboding Victorian home. Two twin brothers, Troy and Bryan, go past her and prepare to vandalize the house, and Adelaide warns them that they're going to die in there. They go inside, smash up things, and then find a freshly-killed possum. The door to the basement creaks open on its own and they go downstairs to investigate. On the shelves are jars filled with parts seemingly taken from babies, Bryan wants to leave and heads up the stairs, but discovers that Troy has fallen behind. He goes to get his twin brother and finds him on the ground, his throat cut open. A white-robed figure charges out of the darkness toward Bryan.
Outside, Adelaide listens as Bryan screams.
Six months ago, Vivien Harmon meets with her gynecologist. He assures her that she's doing better and proscribes hormones. She's reluctant to take any artificial drugs but he assures her that the hormone has no side effects and that it will help her regain control of her body. When Vivien returns home, she hears someone moving around upstairs despite the fact that her husband and daughter should both be out. She calls 911, grabs a knife, and goes up to the room, and is horrified to discover her husband Ben in bed with one of his students. As he comes after her, she slashes at him with the knife and leaves.
Now, Ben, Vivien, their daughter Violet, and the family dog Hallie are going to Los Angeles to start a new life. They joke briefly and Ben tries takes Vivien's hand, but she pushes him away. They go to their new home and meet with the realtor, Marcy. She gives them a tour and explains that the house was built by a doctor to the stars in the 1920s and that the most recent owners, a gay couple, restored it to its current condition. Ben wants to use one of the rooms as a home office for his psychiatric practice, so he can be there for his family. Hallie senses something at the basement door and Violet goes to investigate. She goes downstairs and sees nothing, unaware that someone--or something-- is watching her from the shadows.
Upstairs, Ben comments to Marcy that his wife is a retired cellist, but Vivien refuses to tell the realtor why she quit. Vivien notices a mural beneath a loose piece of wallpaper and is intrigued, and Marcy says that the last owners covered it up. The realtor finally discloses that the gay couple died in a mutual murder-suicide, explaining why the house comes so cheap. Ben and Vivien are reluctant to buy the "haunted" house, but Violet overhears the exchange and immediately tells Marcy that they'll take it.
After their first day of unpacking, Ben suggests that he and Vivien go to bed. She is more concerned about how Violet will get along at her new school, and wonders if Ben can sense how creepy the house is. He assures her that the fact they're getting the house cheap more than makes up for the bad vibes, and tells her that they deserve some good after everything they've gone through. Vivien pulls away from him and thanks him for trying, but warns that it will take time for her to accept him again.
On her first day of school, Violet walks through the courtyard, smoking. Leah and her two friends, Becca and Abby, confront her and Leah tells Violet to put out the cigarette. When Violet stamps it out, Leah starts raging at her and Abby explains that her friend's grandmother died of lung cancer. Leah tells Violet to eat the cigarette butt or she'll beat her, and Violet spits in her face and runs off.
At home, Vivien is peeling away the wallpaper to admire the mural beneath, despite the grotesque nature of the images. A now adult Adelaide comes in behind her and announces that Vivien will die in the house. Before Vivien can deal with the girl, Adelaide's mother Constance comes in. She apologizes for her daughter and sends her home, and then introduces herself as the Harmons' next-door neighbor. Constance explains that Adelaide is obsessed with the house and goes on about how she runs a dog kennel and that she admires Vivien's diamond earrings. She explains that she came to Los Angeles to be an actress but refused to do nudity. When she had Adelaide, Constance was forced to retire. The woman gives Vivien a bundle of sage as a housewarming gift and explains that it is burned to clean out evil spirits, and that there are many in the house.
That night, Vivien burns the sage and carries it through the house. She notices the attic door and goes upstairs, and is startled to find a rubber fetish suit hanging from the rafters. When she screams, Ben and Violet come running upstairs. Vivien says that they need to throw it away and Ben reluctantly takes it out to the garbage.
Ben meets with his first patient, a troubled teen named Tate Langdon. Tate is ready for the "noble war" and that he plans to kill the people he likes so that they will be free of the dirty, impure world, and can go to a better place. He talks about how the Indians used self-inflicted cuts to remove the evil spirits from their bodies, and then blames his mother for his father leaving them because she had an affair.
Violet is in the bathroom cutting herself when Tate comes in behind her. He points out that she left the door open and that if she wants to kill herself, she should make vertical cuts.
That night, Ben wakes up to the sound of indistinguishable voices murmuring to him. He sleepwalks down to the fire place and lights it, and Vivien comes down and asks what he's doing. Ben wakes up and wonders if he's on some kind of acid trip.
Later, Vivien is hanging up sheets to dry in the yard when an elderly woman approaches her. She introduces herself as Moira O'Hare, the housekeeper that comes with the home. Vivien isn't convinced that they need a housekeeper, but Moira says that the house has feelings and Vivien will regret it if she mistreats it. Vivien is still reluctant and Moira asks to come inside to call a cab she can go home. As they wait and have tea, Moira explains that she worked for the previous owners, who fought a lot, and found their bodies after the murder-suicide. When Ben comes in, he's surprised to see Moira as a young, beautiful redhead and that Vivien would hire her given his infidelity. Vivien has no idea why he's surprised since she sees the elderly Moira, and hires the housekeeper. As Moira leaves, Ben tries to kiss Vivien but she pushes him away and he says that someday she'll have to forgive him.
Ben has another session with Tate and accuses him of lying. He says that he'll turn Tate into the police if he thinks he actually plans to harm his fellow students, but insists that everyone can get better. Tate admits that he's met someone but doesn't say who. Afterward, he goes to see Violet in his room. They talk about why they inflict cuts on themselves and Violet tells him about Ben's affair and Vivien's miscarriage. Ben finds them together and orders Tate out, and tells his daughter to stay away from his patient.
Later, Ben is shaving and comes out when he hears Hallie bearing. He discovers the young Moira lying on a couch, masturbating. He stares at her and then goes into the bathroom and does the same. He finishes, crying, and then looks out the window to see a hideously burned man watching from the yard. Ben runs down to confront him but discovers that the man has fled.
When Vivien returns home with groceries, she hears a noise behind her and turns to discover that someone has opened the refrigerator and cupboard doors. Adelaide is in the doorway, giggling, but denies that she opened the door and claims that someone else did it. Unseen by Vivien, the ghosts of the twins step out behind her. Constance comes over to retrieve Adelaide and Ben and Vivien tell Adelaide to stay out of the house. She claims that the twins opened the doors and Vivien grabs her by the head and tells her to promise to stay away. As they go, Adelaide tries to pet Hallie and the dog bites her. The girl says that the dog will regret it and leaves. As Constance goes, she tells Vivien that if she touches her daughter again, she'll break Vivien's arm.
After the encounter been Tate and his daughter, Ben goes to his office and tries to call the authorities to report the boy. The young appearing Moira comes in to dust his office and flirt with him, opening her blouse and unfastening her garter belt. She wants Ben to demonstrate what he did after he saw her on the couch, and starts to straddle his lap. Violet comes in and is shocked to see what she perceives as the elderly Moira on top of her husband. She runs away and Ben briefly goes after her before giving it up.
At school, Leah, Becca, and Abby continues to harass Violet, attacking her in the cafeteria as she lights a cigarette. Violet burns Leah with her cigarette and runs away.
Vivien removes the rest of the wallpaper, revealing the mural in all its twisted glory. Ben comes in and admits that he finds it disturbing, but Vivien says that she finds it comforting. He tries to kiss her again but she shoves him away and he demands to know how long she's going to punish him. Vivien says that she can't look at him without remembering him in bed with his student, and that she's been suffering from the death of her miscarriage. Ben insists that he's suffered as well, and that he tried but failed to get through to her after the miscarriage and only had the affair when Vivien kept rebuffing him. She finally tells him to say how he really feels and Ben says that he was hurt that she bought a dog and slept with it rather than him. He says that he loves her and wants the family to have a second chance, and asks if she wants the same. He tries to embrace her and she shoves him away, and Ben grabs her and they kiss, moving to the sofa to make love. Afterward, Ben says that they're going to be happy in the house.
That night, Vivien is in the kitchen when Violet returns home. She notices her daughter's bruises and suggests they move her to a private school. Violet says that she's not afraid and Vivien apologizes for overlooking her during all of her recent marital problems. However, she says that she and Ben have history together and that they need each other. Violet asks what scares her mother and Vivien says that right now, everything scares her.
Violet secretly meets with Tate and he tells her that if she won't kill Leah, then she needs to scare the girl off. He tells Violet to offer to sell coke to Leah and lure her to the house's basement, and then he'll frighten her.
Vivien is in her bedroom rubbing lotion into her legs when a man in the rubber suit enters. Vivien assumes that it's Ben back for another round of sex, but is surprised since she thought he threw the suit away.
Ben sleepwalks to the kitchen and turns on the gas stove, and then prepares to put his hand into the flames.
The rubber man makes love to Vivien.
Constance enters the kitchen and stops Ben from burning his hand. She tells him that it isn't time yet and that he should enjoy the house and go to bed. Ben walks back to the bedroom and gets into bed next to the dazed Vivien. When she says that she loves him, Ben stares blankly into space and says that he loves her as well.
Violet brings Leah to the house the next day, claiming that she has drugs, and takes her down to the basement where she claims to keep her stash. She leads Leah into the back room with the shelves and finds Tate waiting for them. Tate calls Leah a coke whore and tells Violet to turn off the lights. When she does, the lights strobe and he laughs hysterically, and the image of a skull tattooed onto his face appears. The white-robed figure, its fangs glistening, leaps at Leah and bites her while Tate stands over it. Frightened, Violet turns on the lights and discovers that Tate is back to normal, quietly sitting down, and there's no sign of the white-robed creature. Leah, her face bleeding from a bite mark, runs out of the house. Violet asks Tate what he did but he says that he didn't do anything to Leah. She shoves him away and yells at him to get out. As she runs upstairs, Tate yells after her, saying that he thought she wasn't afraid of anything.
Ben is jogging when the burned man from the yard drives after him. He follows Ben onto a jogging trail, but Ben gets behind him and demands to know what he wants. They sit down together and the burned man introduces himself as Larry Harvey. He explains that he has inoperable brain cancer and was released from prison as a result, where he was imprisoned for the murder of his wife and two daughters. Larry explains that he and his family lived in Ben's house, and that the voice of the house compelled him to set his wife and daughters on fire while they slept. He then stood there and watched them burn, unaware of what he was doing until the flames engulfed him as well. He asks if Ben has had blackouts and tells him to read the trial transcripts. Ben threatens to have him committed if he doesn't leave his family alone and runs away, and Larry smiles in satisfaction.
Constance slips into the house and goes up to the bedroom. As she tries on Vivien's diamond earrings, Moira comes into the room and tells her to get out. Constance refuses, saying that if anything is missing then the Harmons will blame the new housekeeper. She tells Moira to move away so that she doesn't have to kill her again.
When Vivien returns home, she finds Ben in the kitchen. They discuss what to get for supper and she says she wants Indian food. When he points out that she only wants Indian food when she's pregnant, he realizes what she means. Vivien smiles and gives him the news that she's pregnant, and the couple embrace.