In winter, the Metropolitan Police Department received the disappearance of Dr. Akamizawa, and his assistant Usui came to ask for help. At the same time, an unconscious old man and a suitcase he was suspected to be carrying appeared on the Ikebukuro Station tram. It was later discovered that the old man might be the doctor. After the doctor was picked up, Usui took away his suitcase. After that, strange stories about the briefcase spread in Tokyo. It sometimes floated and sometimes disappeared, causing many strange things. Detective Homura Roku intervened in the investigation, and he found many doubts, such as the unknown identity of the advertiser of the briefcase. In Dr. Akamizawa's research institute, Section Chief Homura and Tiannabe witnessed Oyama's strange behavior. Then a fire broke out in the institute, Oyama died, and key figures disappeared. What kind of conspiracy is hidden behind this? What is the connection between a briefcase and a PhD's research?
