A mysterious assault in a locked, double-fastened chamber next to a scientist's laboratory prompts an eighteen-year-old reporter to investigate. He applies careful observation, staged reconstructions, forensic reasoning, and interviews to resolve contradictory testimony and misleading clues. The narrative alternates on-site inquiry, surveillance, and courtroom scenes, exposing rival expert claims, household secrets, and inventive mechanical possibilities. Scientific speculation and methodical detection drive a classic locked-room puzzle toward a precise, surprising explanation of how the crime was committed and why.