Death of a Champion (1939)

Oliver Quade is a pitchman who follows state fairs that feature dog shows---which limits his territory more than a little---at which he sells encyclopedias...and does it well as he possesses a photographic memory that amazes the rubes. The Champion, in the title, is a Great Dane who has won the title at the Rubeville State Fair, and it isn't long before the Champion turns up dead, which is because somebody---motive unknown at the moment---has killed the Champion. This is repeated at other shows along the way and Quade's bright young assistant, "Small Fry", fancies himself as an amateur detective, and starts nosing around into the mystery and drags Quade along with him.