The story takes in 1937, after the fall of Shanghai during the Japanese invasion. Spy Lin Xiang (Aaron Kwok) was ordered to infiltrate Shanghai and reconstruct the underground headquarter that was destroyed. Here he was assigned a simple but with a very strong sense of justice girl, Lan Fang (Zhao Liying), to play his wife. Known as the “underground party couples”, the two fight hand in hand to gather information and fight against the Japanese invaders, notably the Japanese official (Zhang Lanxin).