To make his Crown Princess, Shen Ruyan, smile, Gu Changfeng, Crown Prince of the Great Zhou Dynasty, led his troops in slaughtering the entire Northern Border Fox Clan. Bai Susu, the last surviving orphan of the Fox Clan, narrowly escaped death. To avenge the bloodbath that destroyed her people, she offers the blood of her fallen clansmen as a sacrifice, activates the Fox Clan's forbidden art, grows nine tails, and transforms into human form. After arriving in the capital, Bai Susu learns that Crown Prince Gu Changfeng has been plagued by nightmares every night and that no treatment has worked. Seizing the opportunity, she enters the Eastern Palace under the guise of a female physician. Using the Fox Clan's naturally bewitching charm and her extraordinary cunning, she gradually drives a wedge between the Crown Prince and Shen Ruyan. She also joins forces with Fan Xuan, a prince of an enemy kingdom, to devise a series of elaborate schemes and gradually dismantle the Shen family's political power. Gu Changfeng accidentally discovers Bai Susu's true identity, but having fallen deeply in love with her, he chooses not to expose her.