Casey, a lonely teenage girl living with her single father, begins her journey by sitting in front of her laptop camera, preparing to introduce herself and expressing her desire to participate in the viral "World's Fair challenge." After dimming the lights in her room save for her desk lamp, she approaches the camera with a stuffed toy lemur, which she names "Poe," declaring that both she and the toy will take on the challenge. With uncertainty in her voice, she states, "I don't know what to expect." She proceeds to turn off her lamp and, while staring intently into the camera, recites, "I want to go to the World's Fair" three times, punctuating the ritual by piercing her finger with a pin and smearing her blood on the laptop screen. In a haunting manner, she watches a video filled with colorful strobe lights, her unblinking gaze fixed on the screen, before promising her viewers to give updates on any changes she might experience.
As Casey delves deeper into the World's Fair challenge, she stumbles across various other videos. One features a young man who insists he's "turning into something," while another boasts a mysterious, distorted voice inviting the viewer to the "internet's scariest online horror game." The voice ominously warns, "we can't be held responsible for what you become," suggesting that the challenge is in fact an elaborate alternate reality game. Casey watches a clip of a man who claims there's a game of Tetris happening inside him, alongside a video from a user named Keith who expresses, "I can't feel my body!" as he mindlessly slaps himself while running on a treadmill.
At home, resistant to sleep after being reprimanded by her father for her late-night viewing habits, she expresses her fascination with horror movies and her childhood sleepwalking experiences in another video. Casey's actions grow increasingly erratic as she begins recording herself sleep, ventures into her father’s barn to steal a shotgun, and watches an ASMR video that soothes her after a nightmare.
The tension escalates when she receives a message from a user named JLB, who warns her about the darker aspects of the challenge. In their Skype call, he suggests that the challenge may alter her subconscious. Throughout their correspondence, Casey conveys her unsettling experiences, confessing that she feels as though she is "leaving her body" and transforming into someone else.
The film takes a chilling turn, with Casey's mental stability deteriorating as she uploads a series of disturbing videos documenting her disconnection from reality and increasing anxieties about her existence. In one especially nightmarish video, she wakes up to find herself crawling towards the camera, eerily stating, "I see you there, even if you won't show your face. You can't stop me," possibly directed at JLB, who is shown watching her from a distance.
As the narrative unfolds, Casey’s mental state fluctuates dramatically, revealing her struggles with her father’s estrangement and her desires for freedom from her confining realities. The film culminates in a haunting revelation of her life post-challenge, where she meets JLB after a year apart, having spent time in a psychiatric institution. They share a coffee, exchanging experiences and hesitantly discussing the profound connection formed through their struggles.
Ultimately, Casey confesses, “That night, I made it there... into the heart of the fair. But something brought me back. I don't know what it was.” JLB, filled with concern for Casey’s well-being, reveals his ongoing prayers for her safety, leaving the audience to ponder whether the connection they formed was real or a mere figment of their troubled minds. The ambiguity of their meeting leaves viewers questioning the thin line between reality and the digital horrors that haunted them both.
