It's Halloween, and two friends, Shelby and Becca, playfully create a homemade Ouija-board, called a Spirit Box. It's all fun, until they receive a message from a deceased classmate, who apparently committed suicide a few years back. The message claims that she was murdered. The girls do research on the death, looking for clues. Later, Shelby has some creepy encounters with the ghost in the school's swimming pool, and again at the lake where she drowned, and Becca has some vicious encounters of her own. Shelby steals a police file from her dad's office, and finds that the girl, Emily, had been drugged before she drowned. After several attempts at contacting Emily again, the girls get a message spelling the name of their gym teacher, and they realise he might be the one responsible for Emily's death. Shelby breaks into his house, and finds the drugs that was in Emily's system in his bedside drawer, just as he comes home. He finds Shelby and she pretends to have come there because she can't stop thinking about him and subtly comes on to him. He gives in to her advances, and just as he closes in on her, she shocks him with a tazer that Becca had given her earlier, and he falls down the stairs and breaks his neck. Becca comes in and tells Shelby she called the police and she should wait outside. Becca witnesses the teacher's death. A few months later, Shelby visits Emily's grave, and discovers the nameplate is a fake, covering somebody else's gravestone. She calls Becca, who is now in Taiwan, and Becca seems unmoved by Shelby's discovery, and says she remembers that Emily was actually cremated. Shelby then realizes that Becca was behind the whole thing, the Ouija messages, planting the drugs in the teachers house, and most importantly, Emily's death. She however denies that she had anything to do with the ghostly appearances Shelby witnessed, claiming it was just her imagination. Shelby asks Becca why she did what she did, and we see Becca's memory of the teacher flirting with Emily, and a hurt Becca watching from afar. Becca replies: He was mine first, after which she drops the phone, starts her car, and tries opening the garage door, but it closes. Suddenly the cardoors lock, and Becca finds herself trapped inside. The engine starts up and fumes begin choking her. She turns, and finds Emily's horrific ghost snarling at her. Becca dies slowly, as the exhaust's gas envelops her, and Emily's ghost closes in on her.