Yoo Ryeong (Moon Geun-young) becomes a policewoman in order to find her twin sister. She solve cases with her strong sense of justice and does not follow rules. This gets her into trouble. She partners with Go Ji-seok (Kim Seon-ho), who always fight with her over the cases. However, he ends up cleaning up after the problems caused by Yoo Ryung and holds the key to solving the cases. The two of them end up realizing that they care and love each other.