In the early days of the Republic of China in Shanghai, Luo Shanshan (played by Zhen Xi) returned from Japan to study crime forensics and became the first female inspector of the police station. The most important task for her was to find out the mystery of the disappearance of her father Luo Cheng (played by Hou Changrong) five years ago. The partner arranged by the police station for Luo Shanshan happened to be her father's apprentice at the time, the new inspector Liu Fanxi (played by Ouyang Zhenhua). Luo Shanshan accidentally discovered a record of her father, which suggested that the mastermind behind the severed hand case five years ago was the Chamber of Commerce boss Xu Shaolin and the inspector general of the police station Fan Dewei (played by Fang Zige). At this time, new severed hand cases appeared one after another, and one mystery after another was waiting for Luo Shanshan and Liu Fanxi to solve.