Forensic consultant Shen Du has a secret: He firmly believes that his identification error seven years ago resulted in the death penalty for an innocent teacher. Nowadays, a series of murder cases using similar techniques has reappeared, and the same "impossible trace amounts of physical evidence" as in the old case were found on the corpses of the new cases. The police determined that it was a copycat crime, but Shen Du extracted a 37-second sound wave signature from a corrupt organization that everyone ignored.
In order to track down the truth, he must partner with Lu Zheng, the prosecutor of the case and now the person in charge of the new case. A genius carrying a sense of guilt, a criminal police officer pursuing procedural justice, in the whirlpool of old cases being re-examined and new cases being overturned, he discovered that the buried evidence chain pointed to a deceased person - their common acquaintance.
When the sound wave at the 37th second was restored, what came from it was a last word directed at Shen Du: "The forensic doctor is the murderer."
