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.
Fukami, a secretary engaged to company president Kaido, her employer, is invited by his close friends, the Nogis, to a three-day-two-night tour. The tour group is traveling in a luxurious coach to Lake Megami in the Tateshina Plains. On the way, they are disturbed to hear that Shirai, a hostess who was supposed to come along on the tour, has been murdered. And the next day, the body of Hasegawa, another tour member, is floating in Lake Megami...
