An elderly woman, Ume Matsumoto, informed the First Investigation Department that her son Hirasaka, who runs a shoe store, had disappeared. The detectives had a bad feeling which hit the mark, an unidentified drowned body is identified as Hirasaka. Some prime real estate he owned was also mysteriously sold. Suspecting that this is a planned murder and fearing the escape of the criminal, the Department begins to investigate secretly, without creating an investigation headquarters.