Chief Detective KIMURA Denbei, fondly referred to as Smoky Denbei, is a legendary figure at the Metropolitan Police Department. Transferred to Denbei's Criminal Investigation Division 1, Detective KUMADA Tomekichi arrives from the Toyama Prefectural Police. KUMADA is disconcerted by Denbei's position that murderers nowadays do not need a plausible motive, but gradually adapts to Denbei's unusual methods of investigation.