In the early days of the founding of the People's Republic of China, everything was in ruins. Enemy agents who were unwilling to fail were still lurking in secret to create panic and wait for an opportunity to act. In order to uproot this hidden hostile force and win this war without gunpowder, the mysterious intelligence agency 701 came into being. The severe situation currently facing 701 is that a batch of commonly used enemy stations suddenly evaporated, and the rupture of the intelligence chain will bring immeasurable serious consequences. In order to solve the urgent problem, Zhang Xue Ning (played by Zhou Xun), code-named 200, was ordered to go to Shanghai to find an interpreter with special hearing skills. By mistake, He Bing (played by Tony Leung), a blind tuner with superb hearing, was brought back to 701, and relied on his extraordinary hearing to make new contributions. In waves of repeated tug-of-war, this secret war gradually evolved into more and more dangerous.