After her father's murder, Yoon Ji Woo seeks revenge by infiltrating the police under the direction of Choi Moo Jin, the head of a powerful drug ring. As she goes undercover, she partners with rule-abiding detective Jeon Pil Do, while Cha Gi Ho, the head of the Drug Investigation Unit, targets Choi Moo Jin. Meanwhile, Choi Moo Jin’s loyal subordinate, Jung Tae Joo, and former gang member Do Gang Jae, who seeks revenge, add to the complex web of crime and betrayal. (Source: MyDramaList)