Kim Joon, a transfer student of a prestigious high school, is arrested for the murder of one of his classmates. Yoo jin, the top student of his class, was found dead in the woods behind the school and strong evidence and a group of students' testimonies point to Joon, but after some questioning with the police, he is released. Upon returning to the school, he holds the group of students as prisoners in a hidden basement. The students are members of an elite group of students, composed of the top 1% of the school who have access to certain privileges that allows them to keep their ranking high. Dark secrets of the group begin to unfold with flashbacks of how Joon, an ambitious student from an ordinary high school who was desperate to become a member, was asked to perform a series of cruel tasks in order to get in.