Min-wu (Jo Hyeon-jae) is a passionate detective. He happens to meet an intelligent and cold curator Si-yeon (Kim Tae-hui). He falls in love with her at a first sight, while she feels uncomfortable and afraid as gradually touched by his warmth. She is a soldier of the Old Fox Clan who has to carry on a mission. Forbidden by the Old Fox Clan members to fall in love with humans, love for one man is beyond her reach. Another Old Fox Clan member, Mu-yeong (Jeon Jin) has loved Si-yeon, and Chae-yi (Han Ye-seul) has loved him since young, and their love was never returned. They are also characters of tragic destinies. Min-wu is destined to bring justice to his beloved and her clan, and Mu-yeong becomes the head of the Old Fox Clan. Si-yeon confused between her love and mission, Chae-yi is never afraid of death to get her love. What will their crossing love end up with?