The Florentine Dagger. Ben Hecht

This Golden Age mystery novel features a nervous cavalier with frightened eyes, a mysterious and puritanical satyr, a dagger, a candlestick, a crucifix, and a false beard—and, of course, a detective! (Not to mention the protagonist, «Prince Julien de Medici – of Broadway.») Adapted into the movie of the same name in 1935.