Crossover Cover: The Slype

Some residents of the city of Dullchester find a letter written by Mr. Mipps to Captain Collyer in 1805, which supposedly gives the location of a treasure, and engage in their own treasure hunt until they discover it is a fraud. This novel by Russell Thorndike is connected to his Doctor Syn novels, and therefore to the Crossover Universe. Mr. Mipps is Doctor Syn’s assistant, while Captain Collyer was the villain of the book Doctor Syn.