This is a story about the investigation of a mysterious crime that occurred in 1930s Shanghai. There are no clues or witnesses, only an empty bank vault. Detective Lo Fei, known throughout the country for his unique method, takes on the case. He never rushes and prefers to wait for the criminal to make a wrong move. A young police academy graduate named Qin Xiaoman becomes the genius detective's partner. Together, they uncover a connection between the robbery and a decade-old case.