The Harmon family moves from Boston to Los Angeles to escape their troubled past, and make their home in a house with a past far more troubled.
Two red-headed twin boys are looking to vandalize a house with baseball bats. They arrive on the property and encounter Adelaide Langdon outside, who warns them not to enter the house. She tells them that they will die in there. The boys brush off this warning and proceed to enter the house. They work their way through the rooms, smashing wood and glass. After descending to the basement, they find a number of specimen jars containing animal remains and human fetuses, as well as bloody surgical tools. Bryan complains about the smell and starts to climb back up the stairs. He pauses when he realizes that his brother, Troy, has gone silent. Bryan walks back downstairs to find Troy gasping for air, his throat slit by the Infantata.
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Recently pregnant Vivien Harmon is undergoing an examination by her OB/GYN, Dr. Day, who is trying to convince her to take hormones to increase her sex drive. She refuses, explaining her suspicion that her lack of drive might be a symptom of depression and alludes to her recent stillborn baby. Vivien returns home and is alarmed by noises coming from upstairs. Believing that there is an intruder, she dials 911. Vivien arms herself with a kitchen knife and sneaks upstairs, and discovers that her husband, psychiatrist Ben, is having an affair with one of his students.
The Harmon family, Ben, Vivien, Violet, and their dog Hallie, head to Los Angeles, California for a fresh start and arrive at the same house where the twins were killed decades earlier. While the realtor, Marcy, relays some of the house's history, Hallie starts barking uncontrollably at the basement door and Vivien instructs Violet to check on her. Marcy discloses that the previous owners, a gay couple who restored the house to its original grandeur, died during a murder/suicide in the basement, intriguing Violet.
The Harmons unpack and move in, but Ben and Vivien are continuing to have marital problems. Violet is struggling to adjust in her new high school and is regularly harassed by a trio of older classmates led by Leah after she is caught smoking. Vivien receives a surprise visit from her intrusive next door neighbor, Addy, and her mother, Constance, who gives her a housewarming gift of sage. While burning it, Vivien finds a bondage suit hanging from the attic ceiling. She asks Ben to get rid of it.
Ben begins sessions with Tate Langdon, a young man with vivid fantasies about killing his classmates. Oddly in his fantasies, he kills the classmates he likes. Violet begins self harming and Tate befriends her.
Ben begins sleepwalking while he's nude and begins to hear voices. He lights the fireplace downstairs and is discovered by Vivien.
Vivien is hanging laundry when she is approached by Moira, whom she sees as an older woman in traditional French maid's uniform and who was the housekeeper for the previous owners. Moira's intimate knowledge of the house on how to care for it and its history leads Vivien to hire Moira as a housekeeper. Ben meets Moira in the kitchen, and he perceives her as a seductive, young woman in a much more revealing version of the same attire.
Ben expresses concern about Tate but is confident he can be treated. Unbeknownst to Ben, Tate has since formed a strong bond with Violet and is furious when he discovers them and demands that he leave.
Ben walks in on Moira masturbating in a guest room. In his bedroom, he himself masturbates by a window and starts to cry. He is startled by a man shouting and looks down to discover he is being watched by a man with severe facial scarring, standing on the front lawn. Ben pursues the man but does not catch up to him.
Vivien is unloading groceries in the kitchen and finds the cabinet and refrigerator doors have suddenly opened on their own. Addy giggles from another room, and sees the twins emerge behind an unaware Vivien. Vivien asks Addy to stop entering the house uninvited and makes sures that they are clear she should never come in the house uninvited again. Addy says okay and tries to touch Hallie before leaving who bites at her, angering her. Constance threatens to harm Vivien if she ever touches her again.
Over the phone, Ben tries to report Tate, but is unsuccessful, as he does not have correct and complete information on Tate's background and is then distracted by Moira. They are discovered by Violet.
While restoring the music room, Ben attempts to seduce Vivien after she uncovers devil-themed paintings. They argue over her inability to forgive Ben for cheating and reconcile through sex for the first time in almost a year. Later that night, as Vivien prepares for bed, she sees a figure in the doorway in the rubber suit from the attic. Believing it to be Ben, unaware that Ben is sleepwalking downstairs, Vivien and the man have sex, and Ben is saved by Constance from burning himself on the stove while sleepwalking.
Tate and Violet plan to scare Leah after a physical altercation at school. Violet lures Leah into the basement of her house with the promise of drugs. Tate is waiting there, and as Violet watches, Leah is attacked by the Infantata. Leah runs away, her face deeply cut after the incident. Violet argues that Tate took the prank too far and orders him to leave.
While out on a morning jog, Ben is followed by the burnt man, who introduces himself as Larry Harvey, a previous owner of the house. Larry claims to be on release from prison due to a terminal and inoperable brain cancer and was apprehended after incinerating his family. He was left with burn scars on over 70 percent of his body as a result, compelled by the same whispering voices that Ben has been hearing. Ben threatens to commit Larry if he does not leave his family alone.
Moira catches Constance going through Vivien's jewelry box and, Constance responds by threatening Moira that she'll kill her again.
Vivien comes home and tells a joyous Ben she is pregnant.
- Adelaide: "Excuse me: you are going to die in there."
- Vivien Harmon: "The light is different out here. It's softer."
- Adelaide: "You're gonna regret it."
- Constance: "Don't make me kill you again."
- Violet: "So we're the Addams Family now."
- Leah's friend Becca is played by Christian Serratos, who now plays Rosita Espinosa on "The Walking Dead".
- The end titles are sporadically inter-cut with images only a few frames at a time.
- Vivien looks over Ben's shoulder after telling him she is pregnant and sees Rubber Man.
- Violet's face, in close up, horrified.
- Larry, staring up through the window.
- Addy, laughing at the Twins.
- Larry, driving after Ben.
- A mobile, made from dolls hanged from nooses.
- Vivien, having sex with Rubber Man.
- Moira's masturbation, and Ben's subsequent masturbation.
- Constance threatening Moira.
- Troy, covered in blood.
- Vivien, flanked by the Twins.
- The fire set by Larry.
- What is the connection between Tate and the entity in the basement?
- Who is the father of Vivien's baby?
- Why does Moira appear differently to Ben?
- What did Constance mean when she said she'd killed Moira?
- Who is Rubber Man?
- Is Tate actually alive?