Ning Zhao was once the founding master of the world's greatest assassin organization. Tired of a life filled with bloodshed, she retired and married into the Northern Prince's Manor, becoming a timid heir's wife who could barely bear to watch a chicken being slaughtered. To seize the military commander's seal, Crown Prince Xiao Chengyu forges an imperial decree and leads 300 assassins to surround the manor during the Northern Prince's birthday banquet. He poisons the prince and intends to have the entire household executed. Rather than suspecting Ning Zhao, her parents-in-law, husband, and younger sister-in-law desperately shield her and urge her to flee. When she sees her husband take a blade for her, Ning Zhao finally stops hiding her true identity. With a single whistle, all 300 assassins fall to their knees and acknowledge their master. She turns the tables on the crown prince, saves her entire family, eliminates the traitors, and uncovers the forces behind the conspiracy. Instead of fearing her, her family cherishes her even more. As the heir's wife, Ning Zhao protects the entire household and finally finds a true home.