On the eve of the fall of Shanghai, the missing code book was intertwined with the Japanese secret telegram. Cai Chenxuan was ordered to sneak into an intelligence point disguised as a "bookseller", but Wang Yaqing was forced to change his identity on the same night. While tracing the whereabouts of the secret order of "Shadow in Blood", the two tested each other in a trap set up by traitors: every time they get closer to the truth, they have to pay a price of trust.
