Follows the revenge story of a group of people — including Eun-yong, a money trader — who refuse to remain silent in the face of unjust authorities and fight against a cartel conspiring with the law.

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".