After barely surviving a violent attack by an elusive serial killer, crime boss Jang Dong-su finds himself forming an unlikely partnership with local detective Jung Tae-seok to catch the sadistic killer simply known as "K.

Based on real events that occurred in 2007 dubbed the "Heuksapa Incident". The story follows a turf war that grows between a local gang that runs Garibong-dong in Guro District, Seoul and the Heuksapa gang from Yanbian, China;...