Hwang Ki Joon, Mr Action, and Kang Hee Yeol, Mr Bookworm, are two best friends but contradictory students at Korean National Police University. They accidentally witness a kidnapping and decide to work together to track it down.
Sook-hee is a trained assassin who was born to kill. She was just a little girl when the training started in Yanbian, China. After the death of her mentor, when the chance of starting a new life was given to her, she came to South Korea as a government agent. They promised her that she will be free after ten years of service. So she begins her new life as a theatre actress. But soon two men Joong-sang and Hyun-soo appear in her new life. And she started to find deep dark secrets about her past. Eventually she take matters into her own hands.
Jae-ho has established his own rules and put all of his fellow inmates under his control in a penitentiary facility. After he meets a newly imprisoned inmate, Hyeon-soo who won't give in to anyone under any circumstances, Jae-ho pursues his new ambition to become the boss of his organized crime group once he is released from the prison.