In March 1940, the Wang Puppet Government was established. The Japanese invaders in Shanghai were hunting down anti-Japanese patriots. The Wang Puppet Government set up a "Special Operations Department" headed by former Kuomintang officer Bi Zhongliang to help them. Chen Shen, a member of the Communist Party of China code-named "Sparrow", who had been lurking beside Bi Zhongliang, temporarily lost contact with the organization. In a dangerous situation where tigers and wolves were watching, Chen Shen had a firm belief and risked his life to rescue his superior "Prime Minister" and anti-Japanese patriots. Bi Zhongliang was cunning and treacherous. Although he was "as close as brothers" to his savior Chen Shen, he became suspicious of him and set many traps to press him step by step. After the death of "Prime Minister", Chen Shen finally found a new superior "Doctor" and was ordered to get an important battle plan code-named "Return to Zero" by the Japanese army. Chen Shen's former lover Xu Bicheng and another Kuomintang intelligence officer Tang Shanhai pretended to be a couple and lurked in the Special Operations Department, creating trouble and crises for Chen Shen in many operations. Chen Shen, a man of extraordinary wisdom, was caught in a series of murderous plots. He cleverly used the subtle gaps between the Japanese devils, the Wang Puppet regime and other factions, and at the same time paid a huge price. He finally successfully obtained the "Zero" plan and thwarted the conspiracy of the Japanese invaders.