Six years ago, a massacre occurred in Jintian Building in downtown Binjiang. Entrepreneur Zhang Mingyuan and his family of three were murdered. Wang Haochen, then the chief of the criminal investigation section, led the investigation and located the suspect Li Jianguo. However, the key physical evidence "bloody knife" was accidentally damaged during the transfer process, and Li Jianguo was released due to insufficient evidence. Not long after, Li Jianguo "accidentally" drowned, and the case became unsolved. Wang Haochen took the blame and resigned and was transferred to a lower-level position.
After returning to the Serious Case Detachment, Wang Haochen successively discovered clues related to the cases of the year while handling unit cases. As one case after another was solved, the truth of the year gradually emerged.
