some people say that in jungnim high school, a murder was comitted on the roof. some people don't believe it, but most do. the teachers don't answer questions about it, and they don't speak about it. but aside from that, what makes jungnim high school so unique? well, it's not. Seo Hanji had been sent to jungnim high, after her grades were too low to enter the school she had wanted to go to. A naturally reserved, snobby person, she didn't want to associate with anyone. however, her best friend, Lee Hyojin, is also enrolled in the school, jungnim high school being her ideal.

there are others in the school as well. There's Go Narae, a stuck up social media freak and social butterfly. Lu Rin, a transfer student from china, occupanied by her twin brother, Lu Han. Son Seungwan, the blue-haired, pursuasive president of the debate team. Byun Baekhyun, the school heart throb with a major anxiety disorder. none of these people associate, until a bizzare event occurs on the locked away roof. what will happen to these teenagers when the horror of jungnim high school suddenly comes to life?