Sherlock Holmes receives an encrypted letter from a certain Porlock associated with Professor Moriarty, the organizer of many crimes. The great detective must solve a mysterious murder in England, but discovers that this is only the tip of the iceberg which leads to another story in Vermissa Valley in the United States.This story introduces the character of Professor James Moriarty, the elite criminal mastermind, for the first time in the series. This is the fourth and last novel of the iconic detective character Sherlock Holmes. Sir Arthur Conan Doyle wrote four novels and 56 short stories featuring the fictional detective.