In the third year of Huangyou in the Song Dynasty, a large number of people went missing in Sishui County, Zhuojun Prefecture, which caused public resentment and rebellion. Although the county magistrate Zong Chao suppressed the rebellion, the missing people could not be found. The undercover agent Qiu Xinzhi of the Ministry of Justice was ordered by the Grand Marshal Lu to replace the assassinated leader of the Sishui Gang Zhou Guang, and collect intelligence through his undercover identity to investigate the missing population case. Qiu Xinzhi infiltrated the Surabaya Gang with an appearance very similar to Zhou Guang, and always felt that there were dangers lurking around him. As expected, Qiu Xinzhi was assassinated just as he started his investigation. So, the undercover Qiu Xinzhi and the head shop owner Xiao Liyuan teamed up to investigate the case, one openly and one secretly. However, due to the complexity of the case, Qiu Xinzhi's wild and unconventional solution to the case, which was like defeating an old master with random punches, gave Xiao Liyuan a headache. After going through many dangerous situations, the case was finally solved. However, Qiu Xinzhi gave up on restoring his identity and chose to continue his undercover career, embarking on the journey of solving new cases.