Princess An Ning, the emperor's elder sister, is bestowed in marriage as the second wife of the Duke of Zhenguo. As soon as she enters the household, she is provoked by a courtesan brought home by the heir. Pretending to be his favored concubine, the woman publicly frames An Ning, while the heir hurls insults at her and attempts to punish her. An Ning reveals her identities as the heir's legitimate mother and a princess, exposes the lies in front of everyone, and summons an imperial physician to examine the woman's injuries, proving that she has made false accusations. When the Duke of Zhenguo returns, he takes his son's side, but the princess stands her ground with reason. She subsequently puts an end to the harassment from the old matriarch and her maternal relatives. In the end, the emperor issues an imperial decree in her support, allowing the princess to secure her authority within the household. The Duke also confides in her about his secret private army, and the two reach an understanding to govern the household together.