After Crown Prince Yi Sun is arrested by his fiancee's brother on his wedding/Coronation day for human trafficking, he is dethroned and receives a death sentence which he escapes from. His fiancee, Kim Jungmyung, is forced to marry his cousin and best friend, Yi Jung who is crowned as King in his absence.

Jungmyung decides to use her position as Queen to investigate the truth about Yi Sun's case with the help of her brother, Dae Young who is the General Commander of the Joseon Army and the same person who arrested Yi Sun.

But what happens when Jungmyung realizes that the matter is more serious than she expects, and has to betray herself and break her principles to accomplish her mission?