During the Anti-Japanese War, underground worker Fu Jingnian (Sun Honglei) had a dual identity as an agent. He and his partner "Shadow" (Xu Jinglei) were originally going to cooperate for the last time, but as the contact person "Echo" (Huang Lei) was captured by Fu Jingnian's boss, the head of the Central Bureau of Investigation and Statistics, Ji Zengen (Alex Fong), both of them faced a major threat. At the critical moment, Shadow sacrificed himself to save Fu Jingnian. The truth was seen by Ning Dai (Gui Lunmei), the adopted sister of Shadow. With in-depth contact and a series of events, Ning Dai and Fu Jingnian fell in love with each other fatefully, but the good times did not last long, and the hatred of the country and family separated the two. After the end of the Anti-Japanese War, Mrs. Ji (Ada Choi) introduced Fu Jingnian to her good sister Lu Qiuyi (Jiang Qinqin). At this moment, Ning Dai appeared again. The dual identity and the entanglement between the Kuomintang and the Communist Party made Fu Jingnian unable to touch the love that was close at hand. The organizational task made him face the most difficult choice in his life. As the civil war heated up, where should he go? This film is director Zhao Baogang's debut film, and the story spans 70 years. It combines spy war and love elements, and interprets the love affair between an underground worker and a dance teacher.