The Second Serious Case Group of the Binhai City Criminal Investigation Detachment is composed of five police officers with different personalities. The team is equipped with top criminal investigation technology and solves bizarre cases under the combined mode of "technology + traditional investigation".
The main line of the story runs through the "Bloody Butterfly" serial murder case. The murderer leaves butterfly specimens behind every time he commits a crime, which is mysteriously related to the unsolved case in which the old detachment captain died twenty years ago.
