Art student Jeong-hwa (Seo Woo) is moving to a smaller apartment by her school when she trips and falls, breaking a small statue on a box. She bends over to pick up the pieces and notices an amulet the shape of a queer mask and decides to use it for her exhibit assignment. After she moves she hears a weird knocking sound next door. She can’t sleep because of the knocking sound every midnight and starts sketching the amulet. One night, Jeong-hwa comes home late and runs into a strange woman with long tangly hair and barefoot in front of the elevator. She gets off without a word and starts knocking next door. Jeong-hwa is terrified, what is going to happen to her?

Chilsung School is for troubled kids. One day, a strange and bleak mood surrounds the school. The teachers turn into zombies. The kids must struggle to stay alive.