«The Memoirs of Sherlock Holmes - The Adventure of the Musgrave Ritual» by Sir Arthur Conan Doyle

"The Adventure of the Musgrave Ritual" is one of 56 Sherlock Holmes short stories by Arthur Conan Doyle. In this frame tale, Holmes recounts the events of a particular case he worked on in relation to a university acquantance, who's domestic staff vanished after secretly reading a family document. The document was in fact a riddle, which- in order to understand the peculiarities of the case- Holmes must solve.