1758, Joseon. Four women are murdered in a single night and palace nurse Hyeon suddenly finds herself thrust into the dark and dangerous world of court politics, when all she wanted to do was keep her head down. The prime suspect is none other than, Nurse Jeongsu, Hyeon's closest friend and mentor. Determined to prove her beloved teacher's innocence, Hyeon launches her own secret investigation which runs her into the path of Eojin, the young police inspector who has been assigned to the case. As evidence begins to point to the Crown Prince himself as the murderer, will Hyeon and Eojin be able to reconcile their differences and face the truth?