In the 1990s, in Hechang City, Zhongchang Province, Qin Chuan, a grassroots policeman, relied on his own efforts to study and further his studies, and finally became a criminal policeman as he wished. After the heroic sacrifice of his master Gao Jianshe and his good friend Ye Maosheng, Qin Chuan strengthened his determination to defend justice and punish criminals. He participated in the investigation of many cases and gradually grew into an outstanding representative of the criminal investigation team in Zhongchang. The criminal investigation career needs to cultivate new people. Cao Zhongshu, a criminal technology expert specially invited by the Public Security Department of Zhongchang Province, was impressed by Qin Chuan's talent and concentration. The chief criminal investigation expert Wu Yingde accepted Qin Chuan as an apprentice after rigorous inspection. In the process of solving difficult and malignant cases, Wu Yingde, Cao Zhongshu, Qin Chuan, Tao Weizhi, Li Wen, Zhao Fei and other three generations of criminal police worked together to train a group of more modern and professional young criminal investigation police officers through actual combat. The persistence and dedication of the front-line criminal police in the criminal investigation career also infects their next generation, realizing the inheritance of the police spirit.