The prince at the East Palace travels incognito and gets poisoned due to eating inappropriate food. Since the doctors in the royal hospital have no idea how to cure the poisoning, the top medical official, Doctor Long, asks Long Chongjiu to treat the prince. Liu Feichun, an imperial guard is assigned to investigate the case of assassination of the prince. When Liu's investigation goes deeper, Zhen Guogong's attention is aroused. Zheng Guogong is involved in this case and he hires a killer to assassinate Liu Feichun but Liu is saved by Chongjiu. Zhen Guogong has to confess to his crime. With the further investigation, an imperial concubine Min gets involved.