The film opens with viral video footage of two high school boys attempting to break into Room 402 inside the abandoned Gonjiam Psychiatric Hospital, only for their feed to cut out as they disappear mysteriously. Ha-joon, leader of "Horror Times," uses this incident to launch a massive live-streamed ghost hunt on October 26. He sets up a high-tech command tent outside the hospital while sending six members—Ji-hyun, Charlotte, Ah-yeon, Je-yoon, Sung-hoon, and Seung-wook—inside equipped with GoPros, face-cams, and sensors.
To guarantee viewer numbers reach their 1,000,000 target (which triggers major ad payouts), Ha-joon secretly orchestrates staged scares with technicians Sung-hoon and Seung-wook. They use hidden rigging to drop bells and pull cabinet doors shut. However, genuine supernatural forces soon hijack the building. While exploring the lab, Ji-hyun reaches into a square wall opening; an unseen hand grabs her arm, leaving dark, unnatural scratches. Terrified, Ji-hyun and Charlotte abandon the group and flee toward the exit.
Outside, Ji-hyun and Charlotte walk through the dark forest for hours, only to realize they are moving in endless spatial loops, repeatedly ending up back at the asylum grounds. Ji-hyun suddenly stops and becomes possessed: her eyes turn pitch black, and she begins muttering hyper-speed gibberish ("402호 사람들이...") directly into her face-cam. Panic-stricken, Charlotte runs toward what appears to be the command tent, but upon entering, she discovers she has been lured directly into Room 402 inside the hospital. A floating, naked patient ghost emerges from the dark and attacks her.
Inside the asylum, Sung-hoon, Seung-wook, Ah-yeon, and Je-yoon are trapped in Room 402. The physical room shifts dimensionally: water covers the ceiling and floor, and pitch darkness swallows their flashlights. Spectral shadows pick off each member one by one.
At base camp, Ha-joon sees the live viewer counter soaring past 900,000. Refusing to abort the stream despite hearing his crew's screams over the radio, Ha-joon puts on a camera and enters the asylum himself to complete the broadcast. Upon reaching the upper floors, he looks into a window and sees his own dead body hanging inside; moments later, the Director Ghost strangles him to death.
Hidden Meaning of the Ending: The final shot cuts to Ha-joon's laptop at base camp. The view counter glitches out and reveals the truth: the live stream disconnected hours ago when the power failed. The viewer counter was never at 1,000,000—it had been stuck at just 502 viewers all night. The spirits had manipulated the digital feeds, luring Ha-joon and his team to their deaths while the online world saw nothing. The film concludes with the abandoned hospital standing silent in the morning light, as a sacred water bowl offered to the dead spills over—symbolizing that the spirits remain undisturbed and hungry for future trespassers.