Eun-hee is hired as a vice principal at her old high school, where strange things take place in the closed down washroom. High school student Ha-young and So-yeon, who used the washroom as their hideout hear humming in the empty washroom, and believe that a ghost exists inside. Ha-young discovers a flowerpot on the stairs and suspect that Eun-hee is somehow linked to the mystery. Suffering from hallucination upon her inauguration, Eun-hee finds a ghastly figured girl in the washroom mirror and begins to believe that the girl was the one who brought her back to this school…

While investigating the school files, the frightened teacher Mrs. Park startles and calls the young teacher Eun-young Hur, telling her that the deceased Jin-ju Jang is back. The line dies and Mrs. Park is attacked and killed by a ghost. On the next morning, the teenager Jae-yi Yoon waits for her friend Ji-oh Lim, who has the ability to call the spirits, and they begin a close friendship. The abusive and aggressive Mr. Oh, a.k.a. Mad Dog, is the substitute of Mrs. Park and prohibits Ji-oh to paint and compares the performances of the pretty So-young Park and the weird Jung-sook Kim, raising a barrier between the two former friends. Miss Hur misses her former friend Jin-ju, who committed suicide, and while trying to contact her, she discloses a dark secret about the past of her friend and Mrs. Park.