He's the bodyguard her fiancé hired. She's the vigilante he swore to take down.

In the early Joseon dynasty, noblewoman Lee Chin Sun excels at wearing masks. Not only is she an outlaw fighting for justice, but she's also secretly a gumiho, a nine-tailed fox shapeshifter with a kiss that can kill. But masks are hard to maintain, especially after her fiancé hires a bodyguard to hunt down her alter ego. And when a violent confrontation ends with her guard unknowingly swallowing the source of her magic, she fears a kiss is the only way to get it back.

Park Hyun Soo has hit rock bottom. Wrongfully discharged from the king's service and disinherited, he's on a mission to restore his reputation by killing the infamous vigilante threatening his friend's fiancée. Except Lady Lee is far from helpless, and the vigilante has him questioning if he's fighting on the wrong side.

As Chin Sun does her best to retrieve her magic and Hyun Soo's walls begin to cave to the fascinating beauty, a greater enemy stalks them from the shadows. Chin Sun's magic could be devastating in the wrong hands, and if they don't find a way to work together, a stolen kiss will be the least of their worries.