Meng Siyuan transmigrates into a book as the wicked mother-in-law of the original heroine, Bai Siyao. To save her own life, she immediately reveals that her adopted son, Mu Wenzhou, was born to a Yangzhou beauty, hoping to cast him out of the family once and for all. But a palace messenger arrives with the truth: Mu Wenzhou is actually the emperor's illegitimate son. Left with no choice, Meng Siyuan warns him and lets him stay.
After learning who he is, Mu Wenzhou is manipulated by his concubine, Man Niang. While Meng Siyuan is away, he spends every last coin in the household buying numerous women, whom he tortures to death, claiming he is simply getting an early taste of what it is like to have the emperor's three palaces and six courts. Furious, Meng Siyuan reports him to the authorities, only for the emperor to reprimand her and make her kneel. Bai Siyao steps in to help, sparing Meng Siyuan punishment, and together they ensure Mu Wenzhou spends three months in prison.
Later, the emperor repeatedly hints that he wants to change the succession, panicking the crown prince. He schemes to make Bai Siyao fall off a cliff, then swoops in to save her like a hero. Bai Siyao is badly injured and remains unconscious, so Zhou Siyuan personally visits her and brings her back. Seeking revenge on her behalf, Zhou Siyuan sets a trap for Mu Wenzhou, the crown prince, and Man Niang. Man Niang and Mu Wenzhou are later killed by the crown prince. Zhou Siyuan spreads the news, prompting the censor to impeach the crown prince, who is then deposed. Zhou Siyuan takes Bai Siyao to the Medicine King Valley. Years later, Bai Siyao wakes, and Zhou Siyuan travels the world with her as an itinerant doctor, treating and saving people.
