In 1936 Shanghai, the bustling French Concession intertwined with the treacherous underworld of its dark alleys, creating a turbulent battlefield for spy warfare. Central to this story is Cheng Qianfan's dual life, unfolding a story of faith and sacrifice as an undercover agent. He is a French Concession police officer, a "flame" of the underground organization, and the "Chenzhou" of the Red Team. From the life-or-death encounter with Lao Liao, to the patient pursuit after witnessing the sacrifice of a comrade, from eliminating the traitorous Japanese spy Lao Mo to infiltrating the secret service, every step is a dangerous one. Set against the backdrop of turbulent times, this story depicts the loneliness and determination of an undercover agent, and furthermore, highlights the revolutionary spirit of sacrificing life for belief in the face of national hatred and family feuds.