When Lin Xian discovered Su Wanqing's identity as a "wind listener", Zhou Linyuan was investigating the Xiafei Road shooting case. The piano string fragments in the fingers of the deceased exactly match the German steel strings in Lin Xian's studio, and the distribution of bullet holes on the wall exactly constitutes the variant symbol of the "Purple Wave" code. Surrounded by the Japanese military police, the three had to use acoustic principles, criminal investigation traces and cryptography to start a triple game - the Morse code under the keyboard keys, the coordinate code in the blood stains, and the resonance of the tuning fork in the sewage pipe. Each choice is related to the life and death of millions of people in Shanghai.
