It tells the fateful reunion of twin sisters Cheng Ruoyun and Chou Yanzhi as they become involved in political affairs upon encountering the young emperor Li Yan.
The eunuchs have gained control of the palace during the reign of Emperor Wenzong of Tang. Hoping to free the nation from their clutches, Emperor Wenzhong secretly plots to assassinate the head eunuch Chou Shiliang, but their plan ends in utter defeat.
Prime minister Wang Ya’s entire household is sentenced to death except for his granddaughter twins who barely escape death. The younger sister who is adopted by the Ziyi Bureau assumes the name to Yu Bing’er. Determined to take revenge, the older sister changes her name to Yanzhi and becomes Chou Shiliang’s goddaughter.
Seven years later, emperor Li Yan ascends to the throne. Li Yan resorts to using the Ziyi Bureau to fight against Chou Shiliang. As a result, the two sisters meet again as enemies unable to recognize their relation by blood.