Let me tell you about the Musgrave Ritual Watson.
So your maid ran away and cannot be found?
I wonder what is in this cellar?
Dr. Watson is upset with Sherlock because of his mess and tells him to clean it up. Sherlock brings out a large metal box full to the brim with papers. To not have to clean Sherlock distracts Watson with a story about a case he solved.
Oh my goodness, Brunton?!
Mr. Musgrave invites Sherlock to his mansion the Hurlstone to come and look for his butler Brunton and his Maid Rachel Howells. Rachel ran away and Sherlock and Mr. Musgrave follow her trail. The trail stops at a lake and the only thing found in the lake was a bag full of a few rusty metal bits.
So thats what happened.
Sherlock Figures out that the Musgrave Ritual is a set of directions. Sherlock and musgrave follow the directions to a cellar where they find a secret door.
Sherlock and Mr. Musgrave found the secret stone door. They open to find Brunton dead and a old wooden box brunton was holding on to.
Sherlock figures out what happened to the maid and how brunton was killed. He also discovers that the contents of the bag are gems and Charles the first's crown.
The maid had helped brunton find the treasure but then trapped him in the cellar after it was found.
The musgraves had the crown and the maid was never found.