In Shanghai in 1941, Chen Shan, a street gangster who made a living by selling intelligence, was accidentally spotted by the Japanese spy chief Yui Araki because he looked exactly like military agent Xiao Zhengguo, and he was involved in a bloody underground war ever since. Yui Araki kidnapped his sister Chen Xia and forced Chen Shan to become a Japanese spy. In order to rescue his sister, he, who is gifted as an agent, can only receive secret special training. He pretends to be Xiao Zhengguo and goes to Chongqing to lurk inside the military command, preparing to steal important intelligence.
