"The Adventure of Black Peter" is a Sherlock Holmes story by Arthur Conan Doyle. This tale is in the collection The Return of Sherlock Holmes, but was published originally in 1904 in the Strand Magazine and Collier's.
Forest Row in the Weald is the scene of a harpoon murder, and a young police inspector, Stanley Hopkins, asks Holmes, whom he admires, for help. Holmes has already determined that it would take a great deal of strength and skill to run a man through with a harpoon and embed it in the wall behind him.