During the isolation period in Shanghai in 1939, Cheng Yanzhou, who was framed by Japanese and puppet spies and became a troupe handyman, accidentally activated the "Spy Shadow Promotion System". With the help of the system's missions of assassination, intelligence theft, and instigation of rebellion, he went from being a useless handyman who was bullied by others, to gradually pretending to be a translator for the Wang Puppet Government, a consultant to the Japanese Intelligence Department, and other multiple identities, wandering among the military commanders, Japanese special forces, the Youth Gang, and the Concession Patrol Room. In the process, he develops bonds with many female protagonists such as the latent female military agent, the daughter of Wang Puppet high-ranking official, and the Japanese anti-war doctor. When completing the ultimate mission of the system "Shadow Sword Bearer", he is also involved in real historical events - sabotaging the Japanese army's "Qingxiang Plan", intercepting the germ warfare intelligence of Unit 731, and finally rewriting the pattern of Shanghai's secret war as a "spy legend".
