In January 1940, a Communist underground operative named Liang Shuo wakes up in a blizzard deep in the mountains, wounded in the head and suffering from amnesia. Following a trail of clues, he arrives in Shanghai in search of his true identity, only to fall into the hands of the Japanese military police, leading him to suspect he might be a member of the Kuomintang's intelligence agency. Meanwhile, agents from Wang Jingwei's puppet regime also approach him, claiming he is the director of the Action Department at No. 76. At this time, the Japanese and puppet government are preparing to host the "Peace and Prosperity Conference." A group of refugee laborers held under tight Japanese control are to be sent to the battlefield following the event, placing their lives in imminent danger. The Communist Party devises "Operation Abyss" to rescue them during the conference. At this critical moment, the operative assigned to the mission, code-named "Qing Shuang", suddenly disappears. Under relentless pursuit by Japanese and puppet agents, Liang Shuo gradually regains his memory and discovers that he is, in fact, "Qing Shuang." Holding fast to his red faith, Liang risks his life and returns to No. 76 to find a chance to rescue his fellow countrymen. He learns that a long-buried list of Japanese spies, untouched for over a decade, is also set to be activated at the conference. To complete "Operation Abyss," he must seize that list. Rallying all patriotic forces around him, Liang Shuo thwarts the Japanese conspiracy and successfully rescues over a thousand refugees.