In 1945, as the War of Resistance Against Japan comes to an end, the Japanese army secretly transports a large number of poison gas bombs to China. Ou Xiao’an, the ace special agent of the military, is injured while escaping from the "810" poison gas research institute. He is accidentally rescued by Tan Moqing, a fellow agent. When he wakes up, he finds that he has lost nearly four years of memory. In the process of exposing the Japanese conspiracy, Ou Xiao’an and Tan Moqing frequently join forces, finally tearing away the mask of the Japanese spies and at the same time identifying themselves as underground party members. However, a greater crisis awaits them. As they do not know where the "810" research data and the hidden gas bombs are. Faced with many dangers and obstacles, how should a group of lonely brave men advance and fight bravely?