Yoon-hee is a dedicated high school class president, yet she is secretly despised and isolated by her envious classmates. Her suffocating reality takes a dark turn when a series of eerie, recurring nightmares of a catastrophic flood engulfing her school begins to haunt her. The line between dreams and reality blurs completely when a mysterious substitute teacher arrives, placing a bizarre, lifelike doll at the back of the classroom—a doll whose unblinking gaze seems fixed entirely on Yoon-hee. As the final bell rings, the students are forced to log into a strange website for a mandatory test. In a flash, the lights die, the doors lock, and the entire class is violently pulled into a dark, inescapable alternate dimension surrounded by the very flood from Yoon-hee's nightmares. Now trapped, they quickly realize that their sinister new teacher and the oversized, terrifying doll are pulling the strings of a twisted game where the price of failure is immediate death.
