Three shootings occur in the prefecture. Comparing the rifling of the bullets in the three cases, CSIC find that they were fired from the same gun. This series of murders shocks society. After detailed investigation, it is found that all the clues and traces of micro-objects point the finger at Lin Shiyao, the investigator in charge of shooting cases. Although the CSIC team and the police find it hard to believe the report, but they trust in scientific forensics, and arrest Lin Shiyao according to the law. They must prove that Lin really has committed a crime, and, at the same time, desperately find evidence that he is innocent.