A young female detective, Kim Yun Hee is told to join the largest mafia group so that the police deforces are able to capture the leader, Park Sang Min as they are very difficult to be captured. But as Kim Haneul and Park Sang Min got closer Sang Min became to love her but Haneul only sees him as a criminal and sometimes an older brother as she is engage with the head of police deprtments son, Lee Tae Hyun but to be accepted by Tae Hyun father she is to go on the mission to be able to capture the leader of the mafia group, DARK.