Teenage friends Victor, Lex, Scott, Nick, and Marcus record a video of them doing a variation of 'The Charlie Charlie Challenge' by having Victor read a passage from 'The Gallows,' the reportedly cursed play that killed high school actor Charlie Grimille. Paranormal activity seemingly plagues the basement. Later, Victor finds Marcus hanged outside with swing set chains. The supposedly supernatural serial killer The Hangman strangles Victor with another chain.Aspiring actress Auna Rue moves in with her prop and dressmaker sister Lisa so she can attend Fellbrook High School, which has a prestigious drama program. On her first day, Auna embarrasses herself in front of Mr. Schlake's class by poorly performing a monologue from 'Return to Thayolund,' a fantasy movie Auna has been obsessed with since childhood. Auna recovers somewhat when schoolmate Cade Parker takes a romantic interest in her.A user named 'almostfamous99' interacts with Auna via chat on her unpopular YouTube channel. Almostfamous99 links Auna to Victor's viral video of having apparently conjured paranormal activity by reading from The Gallows.Desperate to bump up her subscriber base after seeing Victor's video had 16 million views, Auna obtains a copy of The Gallows from the school library. Auna becomes unusually obsessed with the play and later uploads a video of her reading from it.Auna becomes the star of Mr. Schlake's class when she performs a monologue from The Gallows. Auna's video also balloons in popularity after viewers notice a table moving during her reading. Auna records a second reading during which an object flies across her bedroom.Auna and Cade bond during an ice cream date. Cade introduces Auna to his parents, who turn out to be famous actors Craig and Kate Parker.While Cade stops at a gas station, Auna becomes spooked by the brief reflection of a hanging man in the rearview mirror. Two young girls claiming to be new fans of Auna's YouTube channel recognize Auna and ask for a selfie, which is how Auna learns a figure appeared behind her during the second video.Another message from almostfamous99 directs Auna to a Charlie Challenge fan page. There, Auna learns about Charlie Grimille while browsing videos of hanging deaths and paranormal activity.Apparent paranormal activity slams a closet door on Auna's hand. Auna briefly sees The Hangman stalking her in Lisa's home.At a party, Auna and Cade sneak away to a treehouse to make out. Auna becomes entranced and has a vision of The Hangman killing Cade. Rattled, Auna demands to go home when she realizes she had been choking Cade while they were kissing.'Return to Thayolund' suddenly starts playing on Lisa's TV. The Hangman stalks Lisa until Auna returns home.As haunting visions continue unraveling her mind, Auna tells Mr. Schlake she doesn't want to read from The Gallows anymore. Auna somehow still recites a monologue from the play even though she thought she was performing Return to Thayolund.Auna blocks almostfamous99 when his messages turn taunting. Auna also starts watching distressing confessional videos posted by Victor's friend Lex, who reveals a disfiguring mark on her neck similar to one that Auna mysteriously obtained.Lisa follows a rope to a tree outside where she finds her dog hanging dead. Claiming it is hurting them both, Lisa rips up Auna's copy of the play. An argument causes Lisa to lash out by saying Auna isn't talented enough to be a successful actress.Auna unsuccessfully tries to intervene via text when she watches Lex, distraught with suicidal tendencies, prepare to hang herself during a livestream. The Hangman seemingly kills Lex.Auna finds her copy of The Gallows mysteriously returned to her back pocket. Auna performs a passage from the play for NYU talent scout Scott Lamont. As he offers her a full scholarship following her reading, Auna envisions a noose strangling Lamont.Lisa packs to leave for a show she is working on, but her suitcase inexplicably vanishes from her hand and returns to her bed. Paranormal activity violently shakes Lisa's house. The Hangman strangles Lisa.Cade researches the deaths that took place at Beatrice High School. An article suggests invoking Charlie Grimille's name summons the hangman character he was supposed to play in The Gallows. Footage from a police officer's bodycam shows a ghost killing the cops who arrested Pfeifer Ross, the crazed daughter of Charlie Grimille, and her mother. Cade discovers that the two women were committed to a nearby mental hospital.With almostfamous99 still harassing her online, Cade takes Auna to see Pfeifer in hopes of finding a way to stop The Hangman's curse. Pfeifer claims the only way to appease The Hangman is to offer a willing sacrifice to be killed.Cade and Auna are abducted outside the asylum. They recover to find themselves on a gallows with nooses around their necks in a forest. The Hangman appears. A hooded executioner tells the duo they must decide who will be sacrificed.Before Auna can stop him, Cade volunteers. A trap door opens beneath his feet and Cade begins hanging. Auna offers her life to save Cade's. Another trap door opens and Auna hangs.After Auna dies, additional hangmen emerge from the forest. They unmask to reveal Victor, Lex, Cade's parents, and Auna's two fans from the gas station among many other participants in a conspiracy to drive Auna mad. Cade removes his harness. Cade identifies himself as almostfamous99 while addressing a camera to proclaim their cabal executed a perfect Charlie Challenge.