Kim Nam Gil is a Catholic priest suffering from obsessive-compulsive disorder and post-traumatic stress disorder. Due to these conditions, he struggles with anger issues and behaves harshly towards those around him. With his analytical skills and sixth sense, he accurately assesses people. He harbors a secret: he was a high-ranking agent in the counter-terrorism unit of the Korean Intelligence Service ten years ago. Kim Sung Kyun is a detective working in the violent crimes unit. He is a soft-hearted man who easily cries. To hide this vulnerability from others, he pretends to be tough. He also has a secret; three years ago, he was a very aggressive and fiery detective, but after his partner was killed, he became a coward. Lee Honey is a prosecutor working in the Central District Prosecutor's Office. She is incredibly talented, works well with her superiors, and is known for her beauty. She stands with the weak and against the strong.
