This is the first in the series of cases involving Inspector Morimoto and his assistant, Officer Suzuki, a young mathematics graduate from Tokyo University. With over twenty-five years experience, Morimoto is not easily surprised, but the dead man's coin locker is just the first of several surprises that Morimoto encounters in this case. Furthermore, Morimoto is puzzled because he cannot find the dead man's umbrella, and he also wants to know why Special Branch from Tokyo is investigating the dead man's company. Moreover, why does the waitress at the Bamboo Haven restaurant provide a different explanation each time they meet, and is there any connection with the baseball game that took place in the Osaka Dome at the time of the murder?

Everything points to an assassination by the criminal syndicates, but Morimoto and Suzuki are not convinced. Using her powers of deductive reasoning, Suzuki helps Morimoto develop a hypothesis that involves espionage, secretive trips on the bullet train, deception, and double deception. Morimoto knows that a provincial inspector such as himself does not impress the Special Branch investigator--especially not when all Morimoto appears to be doing is collecting umbrellas--but perhaps Morimoto will have the last laugh?