Sherlock Holmes and the Sign of Four

Holmes & Watson investigate a cursed family.

Holmes & Watson receive a letter from an informant who known by the pseudonym Fred Porlock. Porlock is a man well connected with criminals. The letter is written in code, and Holmes determines that the code comes from the words in a book. They decipher the code by page and column and find that John Douglas of Birlstone House is in danger.

Holmes & Watson have one baffling clue to help them track down the crime of an American visitor in London.