In 1945, as the Anti-Japanese War was drawing to a close, the Japanese army secretly transported a large number of poison gas bombs to China. Ou Xiaoan, the ace agent of the Military Control Commission, was injured while risking his life to escape from the poison gas research institute 810. He was accidentally rescued by Qin Moqing, who was also an agent. After waking up, he found that he had lost nearly four years of memory. In the process of exposing the Japanese conspiracy, Ou Xiaoan and Qin Moqing frequently joined forces, and finally tore off the mask of Japanese spies and confirmed their identities as underground party members. However, a greater crisis is also waiting for them. Where are the research materials of 810 and the location of the hidden poison gas bombs? Faced with numerous obstacles, how should a group of brave lone warriors fight.