Lee Han Gyu is an agent of the NIS who is trying to track down a group of North Korean spies who have been assassinating people. Having them almost caught after they murdered a family, they somehow manage to escape again, but this time their identities are known, forcing them into hiding. Years later, Han Gyu is working as a private detective as he lost his job due to the failed NIS operation. During one of his investigations, he accidentally comes across one of the North Korean spies. Thinking that the spy doesn't know who he is, he offers him a job in his organisation. But the spy, Ji Won, knows exactly who Han Gyu is. Will he accept the job offer?