The story takes place in Shanghai in the early years of the Republic of China. Gou Jixiang (played by Li Xiaolu) was a virtuous and diligent housewife, but was involved in an accident. Not only did she become a widow, she also became a key target of suspicion by the police. However, Gou Jixiang did not fall into despair. She burst out with great energy in her small body and partnered with Mao Ruyi (played by Jia Nailiang) to become a heroic female detective. Mao Ruyi's personality has always been careless and muddle-headed. His days are muddle-headed, and naturally there are many contradictions between him and the serious and honest Gou Jixiang. However, as time goes by, when one case after another ends in their hands, Mao Ruyi and Gou Jixiang gradually develop a solid friendship. At the same time, they also discover that Inspector Frank, who has repeatedly obstructed their investigation of the case, hides an amazing conspiracy behind him.