Cho Yeo Hwa has been a widow for 15 years. Her in-laws are the most prestigious noble family in the kingdom. During the day, she leads the life of a widow devoted entirely to her dead husband's memory and rarely ventures outside the gate of her home. At night, Yeo Hwa dons the mask of Hero, who secretly jumps over the surrounding wall to save the helpless. In the process, she crosses paths with Park Soo Ho, a handsome senior officer in the Capital Guard, who quickly realizes that Hero and Yeo Hwa are not who or what they appear to be.