在1948年，特工俞北平（饰演者：陈建斌）被调往青城市，任务是解决所发生的命案。但其实，俞北平面临更大的秘密和危险——他的真实身份正在上级的盯戒下。在青城，俞北平遇见了美军中尉林莎（饰演者：齐溪），但未知的是，她Actually, she is the long-lost daughter of the protagonist.
Meanwhile, his young daughter Xu Danni (portrayed by Zhu Yanmanzi) is in college in the city, entangled in a forbidden romance with a married university professor. At the same time, her relationship with her father is strained due to his special status. Caught between completing his mission, maneuvering around cunning and dangerous enemies, and addressing misunderstandings from family, he finds himself in a bitter struggle.
