Plot
The Paynes, a family of four—mother Rebekah, father Chris, elder brother Tyler, and younger sister Chloe—move into a large suburban house inhabited by a poltergeist (referred to in-universe as the "Presence"). The entire film is presented from the Presence's point of view in a series of long takes.
The Presence witnesses the growing cracks within the family. The parents' marriage is strained: Rebekah is controlling and has been committing an unspecified white-collar crime; Chris is passive and planning to leave her to avoid liability. Rebekah dotes on Tyler, an arrogant champion swimmer, while paying little attention to Chloe. Meanwhile, Chris dismisses Tyler and dotes on Chloe, who is grieving the death of her best friend Nadia, one of two girls in the community who recently died in their sleep. Tyler dismisses the dead girls as drug addicts.
Chloe senses the Presence, which often hides in her closet, and believes it's the spirit of Nadia. Tyler befriends Ryan Caldwell, who immediately shows interest in Chloe. She and Ryan get high and discuss loss and grief, until Chloe breaks down, sobbing as Ryan consoles her. He tells her that she will decide when and where they have sex, and discusses his psychological issues and obsession with control. The Presence makes a shelf in Chloe's closet collapse to stop them from having sex.
Tyler and his friends prank a female classmate, soliciting a nude photo from her before mocking her feelings for one of them. When he recounts the prank to his family, Chloe shows them the photo on her phone and accuses Tyler of being the person who posted it online. Chris is appalled. The Presence furiously trashes Tyler's room, revealing its existence to the rest of the family.
Chris contacts the realtor, who insists no one died in the home, as she would legally have to disclose that, but recommends her sister-in-law, a medium. The medium senses the Presence and notes the antique mirror built into the fireplace mantel helps see into the spiritual plane. She claims that Chloe can also sense it due to trauma opening her metaphysical "door." She adds that the Presence could be trapped in an anachronistic time, confusing past with present. Tyler and Rebekah dismiss the story as nonsense, especially after learning that Chris paid the medium.
Another day, after Chloe and Ryan have sex, Ryan spikes Chloe's juice with a white powder. The Presence knocks it over before Chloe can drink it.
Chloe and Chris have a conversation in which he reveals that he believes Chloe's claims, admitting that despite his former mockery of his highly religious mother, he himself has become more religious with age.
The medium returns and warns Chris that she believes the Presence is here to prevent a future event, something to do with "the window that doesn't open."
Chloe invites Ryan to spend the night at the house while her parents are on Rebekah's business trip, though Tyler will still be at home. Ryan tells her he will dose Tyler with Ambien.
After the parents leave, Ryan arrives, seemingly to hang out and drink with Tyler. He drugs Tyler as planned and leaves him asleep in the living room. He brings another spiked drink to Chloe. Chloe tells Ryan that she no longer wants to have sex with him, but he manipulates her into comforting him over drinks. She consumes the spiked drink and becomes incapacitated. Ryan gloats that he killed Nadia and the other girl and made it look like an overdose. He uses plastic wrap to repeatedly cut off her air supply. The Presence frantically wakes Tyler, who runs upstairs and tackles Ryan, throwing them both through Chloe's bedroom window. The Presence looks out the window to the driveway below, as it had many times before, at the now-dead Tyler and Ryan.
The family moves out of the house. Before leaving, Rebekah senses the Presence and follows it to the mirror. The Presence is finally seen in its reflection, revealed to have been Tyler all along. Rebekah breaks down in grief, and as the rest of the family comes to console her the Presence/Tyler is finally freed from the house to ascend to the skies.
