Kyung-min leaves a message to Jong-suk at a crime scene. Jina delivers the message to Jong-suk. Thus, Jong-suk and Kyung-min reunite through the message for the first time in twenty years.
Two friends in the past were victims of serious school bullying. 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.