In the torrent spanning two eras, an unsolved crime emerged, breaking the tranquility of the small town. The former rebellious boy Zhuang Shu (played by Dong Zijian) became a criminal police officer and was in charge of investigating an old case seven years ago, but the suspects gradually pointed to his father and daughter next door who left fond memories in his childhood. Many years ago, Zhuang Shu and Li Fei used to be close playmates. After the restructuring of the state-owned enterprise, with the death of their parents, the two families gradually drifted apart. As the investigation deepened, a cigarette butt made the case clear, and Zhuang Shu was deeply involved. As the investigation progressed, he gradually discovered that he might be a participant in the case