Samon, who had left his position as a police constable, embarks on a journey. During his travel, he is attacked by a group of masked bandits and sufferes a deep wound on his way back to Edo at the request of Magistrate Toyama. Saved by Dr. Kazumichi, Samon is asked by Toyama to identify an informant among the members of the lightning gang, a group of cruel thieves wreaking havoc throughout Edo. Samon then becomes an assistant to the firefighter squad led by Naito Hayato-masamune. One night, while rushing to the oil merchant Tambaya, who is attacked by the robbers, Samon and his group discovered a trembling young girl Oso who is the only survivor of the massacre and has lost her voice due to terror.