Young Debbie Galardi and Laine Morris play with a Ouija board in a flashback, where young Debbie tells Laine the rules of the board, the most important being not to play alone.
Years later, Debbie and Laine are now teenagers. Debbie is shown playing with a Ouija board, saying “goodbye” to someone with it, and tossing it in a fire. Laine shows up at Debbie’s house to take her to the school basketball game, but Debbie turns her down. Debbie explains to Laine that she found a Ouija board in her house and played alone, but Laine dismisses Debbie's anxiety and the two laugh it off. Still, Debbie insists that Laine go without her to the game. Laine reluctantly leaves, even though she senses something is wrong. Back inside Debbie’s house, Debbie finds the Ouija board in her room, untouched. She is possessed by an unseen spirit and hangs herself. After hearing of Debbie’s death, Laine is left mourning and filled with questions. Choosing to house-sit Debbie’s house while Debbie’s parents mourn their daughter’s death at a friend’s, Laine finds an antique Ouija board in Debbie’s room. She begins to suspect it may have played a part in Debbie’s death.
Enlisting the help of her boyfriend Trevor, along with her friend Isabelle, the three friends decide to use the Ouija board to contact Debbie and say “goodbye”. Joining them later are Laine’s sister Sarah, and Debbie’s boyfriend Pete. During their first time using the board, the group contacts a spirit named “D”, whom they believe is Debbie. The board spells out “HI FRIEND”. Laine and Pete emotionally say “goodbye” to their friend using the board, and the power goes out. The group of teens splits up in the darkness, and Laine and Trevor find the stovetop burner on by itself in the kitchen, and Pete is pushed into a mirror after he sees the reflection of a woman in it. The friends leave disturbed, but happy they said goodbye.
As days pass by, the five teens begin to find the message “HI FRIEND” written in various places. They conclude that Debbie must want to talk to them. They decide to use the board again. This session, however, turns into a horrific nightmare when the friends realize they were never talking to Debbie through the board, rather they were speaking to “DZ”. DZ, through the board, reveals that it had also made contact with Debbie. Looking through the glass window on the planchette (which, in the film, enables you to see any spirits in the room), Laine is able to see DZ’s spirit, who we see as a young girl with her mouth stitched shut. The board spells out “RUN”, “MOTHER’S COMING”, and Laine sees the entity of a woman with black eyes and a gaping mouth running at her through the planchette. The group decides to stop using the board.
Through a series of video diaries, Laine learns Debbie found the Ouija board in her attic. Debbie also broke the cardinal rule of the board: never play alone. Isabelle is also killed the same night when she is possessed while flossing her teeth. Her mouth is sewn shut by the floss. An unseen spirit lifts her in the air and drops her, causing her to smash her head on the bathroom sink, splitting it open. After Isabelle dies, Laine and Pete investigate Debbie’s house to get answers. They find a box of photos in the attic of a family of three: a mother and two daughters. Through online archives, they learn that a young girl named Doris Zander lived in Debbie’s house in the 50s. When she mysteriously went missing, her mother was a suspect. Later on, Doris’ sister Paulina killed their mother and was put into a mental asylum. Reaching out to Paulina in the asylum, Laine learns that Doris and Paulina’s mom was a medium. Miss Zander used Ouija boards to conduct séances, and as the séances grew more intense, she used Doris as a vessel for the spirits to speak through. Eventually, Miss Zander went insane and murdered Doris, sewing Doris’ mouth shut to keep the spirits from talking through her. As a result of this, Paulina murdered her mother. Paulina reveals that Doris’ body is still in Debbie’s house, locked away in a secret room in the basement. If Laine and her friends can find the body and cut the stitches from Doris’ corpse, they could save themselves.
The four teens go to Debbie’s house to find Doris’ body, but are attacked by Miss Zander’s spirit. Laine is eventually able to cut the stitches from the corpse’s mouth, and Doris’ spirit is able to overcome her mother’s spirit. Laine and her friends are now safe. That is until Pete is possessed and killed by Doris’ spirit that same night. Shocked, Laine approaches Paulina desperate for answers. In a twist of events, Laine learns that Paulina had lied to her. Miss Zander was only trying to stop Laine and her friends from using the board. Miss Zander wasn’t evil, Doris was. And now she has been set entirely free.
Turning to her grandmother Nona for help, Laine is told that she must sever the connection she and her friends have made with Doris by burning Doris’ corpse and the Ouija board. Laine texts Trevor and tells him to meet her and Sarah at Debbie’s house. Trevor arrives at Debbie’s house before Laine and Sarah and is killed by Doris by being drowned in Debbie’s pool. Continuing forward, Laine and Sarah go to the basement and start a fire in the furnace. Before they can get ahold of Doris’ corpse, Doris separates the two, dragging Sarah into the secret room. To get Doris away from her sister, Laine plays the Ouija board alone. Doris appears by Laine, grabbing ahold of her arm on the planchette and twisting it in its socket. She begins to possess Laine. Just before she is fully possessed, Debbie’s spirit appears and places her fingers on the planchette, making Laine’s possession stop. Sarah shows up in the room with Doris’ corpse and throws it in the furnace, and Laine throws the board in after it. Doris’ spirit screams, the screams of all of the spirits trapped inside of her. She is then defeated, bursting into ashes.