Su Nian, a rebellious modern girl, accidentally transmigrates into the body of Su Qingyuan, the legitimate daughter of the Minister of Rites in the Great Jing dynasty. Barely of age, she is betrothed to Wei Feng, heir to the Marquis of Zhenbei, a brutal man with a taste for killing. Unable to bear the humiliation, the original owner drowned herself. After taking over her body, Su Qingyuan resolves to escape the arranged marriage and live a free, rebellious life. By chance, she meets Xiao Yu, the capital’s notorious “Demon King of Mischief.” Their equally rebellious natures make them hit it off at once, and they become allies.
With Xiao Yu’s protection and help, Su Qingyuan repeatedly breaks free from the constraints of feudal etiquette: she visits the ghost market at night and wins the Listening Wind Token, publicly gives Wei Feng and an antagonistic noblewoman a piece of her mind at a palace flower-viewing banquet, and exposes Shen Yurou’s schemes to frame her. As her conflict with the Wei family escalates, she uncovers the shocking secret that Wei Feng and his father are colluding with the enemy and betraying their country. To end her betrothal for good and protect the people along the border, she and Xiao Yu plot to sneak into a birthday banquet at the Wei residence and steal incriminating evidence, including secret letters and account books. But Wei Feng corners them in a hidden chamber, leaving them in mortal danger.
