**Time background**: After the Songhu Battle in 1937, on the eve of the fall of Shanghai. This oriental Paris is experiencing the darkest night before dawn. The neon singing and dancing in the concession form a cruel contrast with the ruins of the Chinese border.
- **Space Background**: The story begins in the Xiafei Road Apartment on the edge of the French Concession. It appears to be a tea warehouse for a French trading company, but is actually a secret liaison station for the military. The winding Suzhou River separates the concession and the Japanese-controlled area into two worlds.
- **Intelligence System**: The Shanghai Juntong Station adopts a "honeycomb" structure, and each intelligence agent only communicates with the upper line through a single line. The Special High School infiltrated through "shadow operations" and used a "ground network" composed of radio direction finding vehicles and traitors to carry out three-dimensional encirclement and suppression.
