Cast: Park Hye-min, Yu Seon-dong, Lee Jung-hwa, Park Ji-yeon, Hwang Jung-eum, Kim Su-ro, Yoon Shi-yoon
In Woosung High School, 30 students with outstanding academic achievements will have extra tutoring courses during summer breaks. On the first day, a horrible thing happens. At midnight, passing out and waking up after inhaling some gas, students and teachers hear a mystery man's voice through the speaker. He says that they will survive after answering every question he throws. Students are killed one by one, and the rest gets panicked. Mr. Cha and Eun-soo, the student-teacher, try to calm the students down and find the culprit. Meanwhile, Ji-yeon figures out the connection between dead students, suspecting an incident years ago might be the cause.
