6. The Musgrave Ritual
In this, one of Holmes' earliest cases, a quaint family heirloom, a riddle passed down from generation to generation, turns out to be the secret to finding the lost crown of King Charles I, a secret that results in the disappearance of the family butler and maid. It is partly interesting as an example of Holmes' riddle solving abilities and partly because it is one of the few stories that Holmes himself tells rather than being narrated by Watson. Watson gives a brief narration as a frame device, but the case itself pre-dates him and involves Holmes helping out an old university acquaintance: Reginald Musgrave. Within the BBC series it would be nice to have Holmes recount the details of some earlier adventure or mystery that prove pertinent or similar to their current case. It would help establish more of a sense that Holmes had an existence prior to Watson joining up with him, a world in which he had friends of a sort and began to establish himself as a reliable solver of mysteries (something touched on in the episode The Great Game). Watson would be quite ready to be somewhat disbelieving of the image of Holmes with any friends other than himself, which could be a good source of gentle tension between the two. The ritual itself is something that could be open to some quite loose adaptation while still referencing the original story, the Basil Rathbone film turned it into moves on a giant chessboard. Perhaps, given Holmes and Musgrave's student history together it could become some archaic Oxbridge student tradition that nobody questions the meaning of.