According to the report, a large number of guns have been smuggled into Korea and a new agent, Yoo Da-hee is sent there. Although she had met a "top" agent from the NIS who offered help, his on-site investigation was very flawed and the two started to argue. However, those they have met in order to find clues were all killed and they suddenly became suspects. Facing the uncontrollable crisis, they overcome the difficulties together....