While returning from a business trip to Hokkaido, Detective Kamei of the MPD greets a middle-aged traveler in the waiting room of Minami-Wakkanai Station but is ignored by him. On the limited express to Asahikawa, the same man happens to entrust Kamei with a floppy disk before dying. The floppy contains his investigative notes on a murder that happened two years ago...
Katsura Aya (Shiratori Yasuyo), a young and popular actress, is kidnapped. Igarashi (Honda Hirotaro), the president of the production company, calls Totsukawa (Mihashi Tatsuya) and Kamei (Aikawa Kinya) of the police. Totsukawa and Kamei learn that the kidnapper's name is Aoi Hebi (Blue Snake) and that Aoi Hebi is asking for one million yen for ransom.
Haneda, the president of a company dealing in gold, is shot to death on the Raicho 9 limited express from Osaka to Kanazawa. Detective Kamei begins an investigation in cooperation with the Fukui Prefectural Police. In the Green Car, Detective Nishimoto had noticed a beautiful woman talking to the victim just before he was killed. Looking into her background, she turns out to be Yumiko Miura, living in Setagaya in Tokyo. An eyewitness who claims that she is the murderer also appears, and she is taken into custody. Before long, the victim's unexpected relationships will be revealed one after another...
