1938, Harbin, Heilongjiang, China. Zhou Yi is a Communist Party special agent successfully infiltrated in enemy territory as a high ranking official, and Gu Qiu Yan is an experienced telegraph operator dispatched by the Communists to act the part of Zhou Yi's wife. Together they must face the meticulous and formidable Guomindang special agent Gao Bin, as their true identities may be exposed at any moment. At first the two of them find it difficult to work together, but slowly their relationship begins to evolve.