Park Gang Yoon, Chief of Investigations, is under suspicion of using brutal and corrupt methods to achieve his unrivalled arrest record. When Choi Min Jae, a young officer from a well-known family of police enters the force, his ethical principles bring him to the attention of the department. He is ordered to join the investigative team, monitor Park's actions and report back. Hesitant at spying on a senior officer, Choi agrees without disclosing his real reason for doing so. The young man is on a mission to locate a secret document involving his late father and this could be his chance. As a new member of the Investigations team, things appear to be going well. Working on the case alongside his fellow officers, Choi begins to appreciate and admire his chief even though it is growing obvious that the man constantly crosses the line into the dark side of the criminal world.