The 11th popular series in which Kyosuke Kamizu, a university professor and a famous detective, challenges the mystery of the murder case. A bank clerk Fukushima was killed by a cyanide compound on a crowded train. Newspaper reporter Yamashita and colleague Kaori, who were on board, immediately started interviewing. In addition, Kaori asked Kyosuke Kozu (Masaomi Kondo), a university professor who had previously elucidated the murder of prussic acid by tablets, for cooperation. As a result of the investigation, it is discovered that Fukushima, who was killed, violently attacked a female college student with his colleagues and forced him to commit suicide....