Audiobook The Casebook of Sherlock Holmes I written by Arthur Conan Doyle. These six cases are among the last undertaken by Sherlock Holmes before he retired to the Sussex downs. However, the problems facing the sleuth are as diverse and challenging as ever. With seeking the whereabouts of the stolen Mazarin Diamond, discovering the importance of being called Garrideb, encountering a mysterious murder on Thor Bridge, searching for eternal youth and the threat of a Vampire in Sussex, there is no sign of Holmes’s deductive powers slowing down.