When North Korean secret agent Ji-won crosses the 38th Parallel on a mission to assassinate a traitor, a small task force of the National Intelligence Service (NIS) led by Han-gyu intervenes, leading to messy shooting rampage in the heart of Seoul. For the incident, Han-gyu is fired from his intelligence position and Ji-won is deserted by his agency and country. Six years later, the two former agents, now a private investigator and a construction worker respectively, crosses paths in a chance encounter. Although both men recognize each other right away, they keep their own identities a secret, and Han-gyu talks Ji-won into working with him. As both men work their particular angles, trouble brews again and unfinished business from 6 year ago is about to resurface.