Paige Benedict, a young accountant, moves into a spacious loft in Los Angeles owned by Jonas and his eccentric wife Elaine. Her police officer boyfriend, Mitch, is angry she has moved out of his home and dismisses her dreams of becoming an artist. In the closet, she discovers a Ouija board. While playing, Paige begins receiving messages from an entity who claims to be named Susan. The board initially seems to predict Paige’s upcoming promotion at the accounting firm, and when she questions the tenants, they reveal that a woman named Susan Sidney formerly lived in the apartment.
When Paige tries to contact Susan again via the Ouija, chaos erupts: Jonas is attacked in his shop by a poltergeist that flings tools at him, and he locks himself in the boiler room, only to be incinerated as the boiler overheats. Paige's nights grow darker, filled with nightmares that drive her to paint disturbing images of a woman she believes to be Susan. At the funeral for Jonas, Russel, a fellow tenant and photographer, reveals that Susan was an exotic dancer who prostituted herself to Jonas in exchange for rent. He admits he doesn’t know how Susan died and hasn’t seen her since she was evicted two years earlier. Paige confronts the Ouija again, and the entity repeats that it is Susan, insisting she was murdered.
Paige asks Mitch to search for records about Susan Sidney, but nothing turns up. When Paige vocally challenges the entity through the board, the loft’s shutters slam shut in response. Elaine and Russel offer comfort, but the three of them decide to use the Ouija together to pursue Susan. The board guides them to “uptown”; Mitch mentions a remote area outside the city known as Uptown Woods. Convinced Susan was murdered and buried there, Paige has Russel drive her to the location, only to be intercepted by Mitch, who arrives to escort her back home.
Mitch is later injured in a car hijacking linked to the entity. Russel warns that the Ouija board has long been used by witches to contact demons, though Paige remains convinced she is communicating with Susan. The discovery of an Susan Sidney–related earring deepens the suspicion that Susan is real, not a figment, and Elaine is suddenly killed in a violent accident.
Paige pieces together a troubling clue: the earlier message directing her to “uptown” should have read “Upton,” the name of Russel’s photography company. Realizing Russel murdered Susan, Paige tries to escape, locking herself in a bedroom. Russel attempts to break down the door, but Mitch—now released from the hospital—stops him. In a shocking turn, Elaine is revealed to be the killer, aided by Jonas. Paige then emerges, adopting Susan’s form, and ejects Mitch from the room by throwing him through a window, though he clings to a fire escape. Susan stalks Mitch, attempting to finish him, while she shuttles between her own and Paige’s forms. Mitch pleads for Paige to fight Susan’s spirit, and, at the climactic moment, Paige destroys the Ouija board, freeing herself from Susan’s possession.
