Two friends, Kyung Min and Detective Jong Suk, reconnect after receiving a message from a friend they haven't heard from in 20 years. The message triggers painful memories of their school bullying, and soon after, a series of mysterious murders begin. As Jong Suk investigates, he uncovers connections to the past, while the drama explores the origins of school violence and its enduring impact on society.
Two friends in the past were victims of serious school bulling. One could not resist his trauma, and becomes a serial killer, walking in the path of revenge. Another one tries his best to overcome the trauma and becomes a police detective. He now faces tragic fate to risk his life to capture the serial killer.



