The witty and mischievous Su Duoduo temporarily takes the place of a legal advisor to enter the county yamen, originally planning only to slack off and idle away her days. However, by a stroke of luck, she discovers that a sealed cold case from three years ago is riddled with suspicious doubts. To uncover the truth of the incident, while dealing with the rigid and aloof county magistrate Shen Yanci and dodging his strict supervision everywhere, she secretly gathers various clues. Su Duoduo rallies the head constable, the veteran legal advisor, the jailer, and the teahouse attendant, combining everyone's strength to launch an investigation together. Breaking out of conventional case-solving thinking, she sifts through fine fragments of clues to peel away the fog bit by bit, ultimately unearthing the complete truth that was deliberately concealed behind this old case.