sentences:  The case is investigated by Inspector Richard Queen of the Homicide Squad with the assistance of his son Ellery, a bibliophile and author.The principal clue in the mystery is the disappearance of the victim's top hat, and it is suspected that the hat may have contained papers with which the victim was blackmailing the murderer.A number of suspects are considered, but nothing can be proved until Ellery performs an extended piece of logical deduction based on the missing hat and thus identifies the murderer.