The story opens with an elderly woman trying to unlock a mysterious box. As she plays some vintage music, she gathers holy water and a hammer, preparing to destroy it. However, before she can act, she is forcefully thrown around her room by an invisible entity. When her son arrives, he finds her unconscious on the floor.
We then meet a recently divorced couple, [Clyde](\/actor/jeffrey-dean-morgan) and [Stephanie Brenek](\/actor/kyra-sedgwick), who are navigating life with their two daughters, Em (Natasha Calis) and Hannah (Madison Davenport). Clyde takes his children to a yard sale where Em becomes fascinated by an ancient box inscribed with Hebrew characters. He reluctantly agrees to buy it for her.
As Em carries the box around the yard, she encounters the old woman, now lying in bed shrouded in bandages. Startled by the box, the woman violently slams her hand against the window, screaming until her nurse draws the blinds. Later, Em insists that Clyde open the box, but he realizes it may not be meant to be opened. Ignoring his concerns, Em brings it to her bedroom, where strange whispers soon start to emanate from it.
Curiosity gets the better of her, leading Em to pry it open that night. Inside, she finds a tooth, a moth's corpse, and a ring which she begins to wear with sinister implications. As days pass, Em's demeanor shifts dramatically; she becomes withdrawn, even attacking Clyde with a fork. Her room becomes infested with moths, and one night she has a disturbingly bizarre gagging episode in the bathroom, culminating in a horrifying moment when a hand seems to crawl from deep within her mouth.
At school, a classmate provokes her about the box, prompting an explosive reaction where she violently strikes him. This alarming behavior leads to a meeting with the principal and teacher, who express concern over Em's growing aggression and isolation. The teacher suggests that they keep the box away from Em. However, that night, curiosity proves fatal when the teacher attempts to open the box and is thrown out of a window by the malevolent force contained within.
Em reveals to Clyde that there is an invisible woman inhabiting the box and claims, "I’m special." Disturbed by her revelations, Clyde tries to dispose of the box, but when Em hears of it, she pleads with him, only to be hit by an unseen force, making it appear as though Clyde is being abusive. She finds the box and starts conversing with the dybbuk. In a shocking twist, moths fly out and into her mouth, causing her to faint. Clyde rushes her to the house, where police take her away from him, leaving him to retrieve the box.
Desperate for answers, Clyde visits a university professor who identifies the box as a dybbuk box, dating back to the 1920s, designed to imprison a dislocated spirit—a Jewish demon. He sneaks into Stephanie’s home, trying to perform a ritual to protect Em but is thwarted when she returns.
Clyde then consults a Hasidic Jew, [Tzadok](\/actor/matisyahu), who informs him about the three stages of possession, with the third stage being the dybbuk merging with its host. They discover the demon's name is Abyzou, known as the "taker of children."
Later, in a chilling moment, Em violently assaults Stephanie after gorging herself out of the fridge. It’s suggested that Em should see a psychologist. However, when the boyfriend Brett makes an attempt to transport her, Em stares at him menacingly, causing his mouth to bleed profusely and triggering a frantic escape. Em’s condition worsens, culminating in a seizure on the lawn, leading to an MRI where Stephanie discovers the terrifying visage of the dybbuk beside Em’s heart.
Realizing Em is possessed, Clyde, Tzadok, and the family gather at the hospital to conduct an exorcism. After a harrowing confrontation, Em escapes to the morgue with Clyde pursuing her. In the climax, the dybbuk is expelled from Clyde during Tzadok's exorcism, returning to the box.
In the aftermath, the family finds healing as Clyde and Stephanie rekindle their love. Tzadok drives away with the box in Clyde's vehicle, but disaster strikes when a truck collides with him, suggesting that the horrors may not be over. The box is seen eerily resting a short distance from the wreck, hinting at the lingering evil within.
