Min-Ah discovers a shared diary and is fascinated to learn that two schoolmates she thought to be close friends have, in fact, begun a forbidden romance. Unable to tear her eyes away, the secret allure of the diary begins to consume her. When one of the diarys writers is found dead from an apparent suicide, rumors spread and Min-Ah begins to sense a strange presence. The once tranquil school is transformed into a morbid place of terror, as if the journals words, memento mori (remember the dead), have taken on life.