In the winter of 1941, the Shanghai Concession became an isolated island. Zhou Tianming, an underground party member, was ordered to sneak into the Japanese secret service "Mei Agency". On the surface, he was a traitor translator, but in fact he was an intelligence agent codenamed "Nightingale". He must obtain the Japanese army's upcoming "Qingxiang" plan within seven days, otherwise thousands of soldiers and civilians in the northern Jiangsu base area will be plunged into a sea of blood. However, the traitor's betrayal led to the destruction of the contact station, and his only upline, Lao Chen, left only a code word before his death: 'The sparrows are singing on the wires.' Zhou Tianming had to shuttle between the Youth Gang, the military commander, and the Japanese and puppet spies, weaving a protective network with lies. He found that he was stepping on the edge of a knife every step of the way - the seemingly reliable informant might be a double agent, his childhood sweetheart female teacher was actually a military agent, and the Japanese military police captain always remained suspicious of him. In the early morning of the seventh day, he risked his life and sneaked into the archives of the Mei Agency, but at the last moment he discovered that the "Qingxiang Plan" was just a bait, and the real killer move was a secret experiment of "germ warfare". Zhou Tianming faced a choice: retreat with the intelligence, or go deep into the tiger's den and destroy the laboratory? He lit the final signal flare, and gunshots rang out along the Huangpu River...
