Florentine Dagger

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, &quote;Prince Julien de Medici -- of Broadway.&quote;) Adapted into the movie of the same name in 1935.