On Suyoung is working as an officer of the Royal Pharmacy, and when he finds out about the emperor's plan to behead the king for the treason charges, he feels sympathetic and gives anesthetic potion to the king to lessen the pain. And during the execution, the king thanks Suyoung and curses the emperor as he dies. The next day, Suyoung wakes up in a strange place and realizes that he is living in the emperor's body! Shivering with fear, Suyoung hurries to the Royal Pharmacy and finds the emperor in his body. And from that point and on, a spectacular drama takes over the palace.