Veteran detective Zhou Tieshan wrote in blood before his death: 'The murderer is in your police station. ' Disciple Lin Rui was suspected by everyone, but with the help of Su Yan, he discovered that the encrypted file left by his master pointed to tampering with the internal system of the police station. Forensic doctor Zhao Dequan hid the key autopsy report, deputy captain Chen Zhao wavered between conscience and fear, and inspector Han Xiao suppressed the truth in the name of investigation. When Lin Rui got closer to the truth step by step, he discovered that his master's last words were a trap set with his life - just to let the person who can really break the trap survive.
