Eun-ah is a woman who disguises herself as a man in order to earn a living as hired protection. When she by chance saves a young nobleman from being robbed by some crooks, she quickly learns that the young nobleman was actually the Crown Prince of Joseon, and he wants none other than for her to be his personal bodyguard! Trouble is, she can’t let anyone, not even the Crown Prince, know she’s actually a woman, or her life will be forfeit.