1758, Joseon. Eighteen-year-old Hyun is the illegitimate daughter of a government official. It's hard for someone like her to rise to the top in society. But through hard work and academic success, Hyun manages to get a position as a palace nurse. All she wants is to do a good job and maybe finally earn the approval of her estranged father. But suddenly Hyun becomes an unwitting witness to dark and dangerous political games: someone kills four women in one night, and the main suspect is her close friend and mentor. Deciding to prove the innocence of her beloved teacher, Hyun begins her own secret investigation. In search of the truth, she meets a young police inspector Ojin, who is also looking for the killer. When evidence begins to point to the involvement of the crown prince in the case, Hyun and Ojin join forces. They are ready to search the darkest corners of the palace and put their lives in mortal danger - they are ready to do anything to solve this bloody crime.