On the night of March 14th 2001, exactly one day after the incident at Yeondu High, four individuals return to the school in search of answers to the unsolved mysteries that haunt them. Episode 1: Disturbed by rumours of her involvement in the death of a fellow student, Jung Soo-jin is determined to set the record straight and regain the trust of her crush Jang Sung-tae. But as the pair search for clues, they learn of a far darker secret deep within the bowels of the school, and become prey in a relentless hunt. Episode 2: At the same time, former teacher-in-training Kang Seo-yeon arrives to investigate the ambiguous circumstances surrounding her father's passing on the school grounds. Drawing on her knowledge of the occult, Seo-yeon attempts to reverse an ancient ritual while evading a powerful and malicious ghost that is inexorably drawn to her. Episode 3: Having made a promise that can't be broken, 1st year student Yoo Ji-min searches for a way to bring peace to the restless spirit of Han Na-young. Delving deeper into the tragic history of the school and the complex relationships between its students, Ji-min makes a fateful discovery that will lift the veil of obscurity once and for all.