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Holmes' former college acquaintance, the aristocrat Musgrave, turns to the detective about the mysterious events taking place in his castle. The other day, the butler was spotted secretly looking through a family document called the Musgrave Family Rites. The owner wanted to fire the butler for such blasphemy, but he suddenly disappeared.

A servant who had an affair with the missing man goes crazy and suddenly disappears. Holmes believes that the document the butler was interested in is important to the case, as the butler risked a good job by going for it.