When the famous SL "Lady of Childbirth" traveling on the Yamaguchi Line approached Tsuwano, a passenger saw a man crashing into the tracks from the top of the Usui Tunnel. When the conductor rushed to report it, the man was already dead. Shortly after, the witness passenger had disappeared for some reason! Detective Sato (Takuma), who rushes to the scene, learns that the dead man is Odagiri (Odagiri), a taxi driver whom he met earlier.