In the third year of the Huangyou era of the Song Dynasty, in Sishui County of Zhuojun Prefecture, a large number of people went missing, causing public resentment and leading to a rebellion. Although County Magistrate Zong Chao suppressed the uprising, the lost population could never be recovered. An undercover officer from the Ministry of Justice, Qiu Xin, was ordered by the Grand Commandant Lu to replace the assassinated leader of the Sishui Gang, Zhou Guang, and to gather intelligence through his undercover identity in order to investigate the missing population case. Qiu Xin used his striking resemblance to Zhou Guang to infiltrate the Sishui Gang, always feeling the threat of assassination looming over him. As expected, he was soon targeted for assassination as he began his investigation. Consequently, undercover Qiu Xin teamed up with the gang leader Xiaoliyuan, working both openly and secretly to solve the case. However, due to the complex and confusing nature of the case and Qiu Xin's unpredictable and chaotic approach to solving it, Xiaoliyuan found himself plagued with headaches. After going through many dangers, the case was finally solved, but Qiu Xin chose to abandon his identity recovery and continue his undercover life, embarking on a new journey to solve further cases.
