Childhood friends Chen Ke Hai and Fang Li went their separate ways and found themselves in the No. 76 secret service. In 1939, the Bureau of Investigation and Statistics created a special class to combat the No. 76 of Wang Jing Wei's regime, with the hope of resisting Japan. Chen Ke Hai, now a secret member of the Communist Party, returns to Shanghai with the mission of infiltrating No. 76, where Fang Li is the leader. The brutal experiments reveal the truth about the bureau. Chen and Fang are separated after a failed assassination attempt. Facing a drastically different Chen Ke Hai, Fang Li tests him and places an agent at his side. Chen Ke Hai struggles to convey valuable information to his party without backing down. After the war, the former colleagues have a final confrontation over their contrasting beliefs.