Yuan'an County Magistrate Nan Ruiyang was assassinated on his way to Beijing. His sister Nan Biyue disguised herself as a man and went to Beijing to pretend to be Nan Ruiyang. She secretly tracked down the murderer of Nan Ruiyang. During the process, she met the shady Prince Zong Zhengli and the gentle and jade-like Jing Wang Zong Zhengheng. With Nan Biyue's investigation, the murderer of her sister-in-law many years ago, the assassin of Nan Ruiyang, and Chun Wangjing's father all pointed to one person, and the truth slowly emerged.