After the victory of the Anti-Japanese War, Gu Yaodong (played by Li Yifeng), a top student of the law school who grew up in a Shanghai alley, graduated from university with the ideal of "supporting justice and protecting the people". However, Gu Yaodong, who had just entered the workplace, not only encountered the exclusion and suppression of his colleagues in the police station, but was also involved in the fierce struggle between the Communist Party's underground intelligence network and the Kuomintang police. In the turbulent times, Gu Yaodong had to make a choice to be loyal to his beliefs in the confrontation between justice and injustice. In the end, with the help and training of the Shanghai Underground Party Police Committee of the Communist Party of China, with Xia Jicheng (played by Wang Longzheng) and Shen Qinghe (played by Jin Chen) as the backbone, he fulfilled his ideals in the journey of revolution and also gained precious love.