The Musgrave Ritual

Holmes - somewhat reluctantly, and incidentally on drugs - takes Watson to visit his old school acquaintance Reginald Musgrave, the scion of one of the oldest families in Sussex. Musgrave's butler has been acting very strangely, and there's an ancient document - a ritual - that has haunted the family since the 17th Century. Can Holmes and Watson solve the case? Of course they can - that's a given. But what else is entailed? That's the fun part.