In Shanghai in 1941, mathematics teacher Zhang Lushi was a member of the underground intelligence organization "Nightingale". After the arrest of "Old Zhong" on the line, Zhang Lu contacted military special agent Su Wanning and discovered that their fates had been intertwined as early as the Nanjing Massacre. Zhang Lu cracked the Japanese military's "Sakura Project" bacterial weapons intelligence, but was rounded up by the spy chief Ichiro Sato. In prison, he discovered that Sato was an undercover anti-war agent and teamed up to sabotage the transportation of bacterial weapons. Cheng Mo died during the operation, and Su Wanning was transferred from Shanghai. When the Anti-Japanese War was victorious, the two were separated in the explosion, and the pocket watch signal hinted that a new spy war was about to begin.
