Dr. Watson is talking to Sherlock Holmes at 221 B Baker St. London, Watson asked Sherlock to clean. Musgrave went to Sherlock for help about business at the Hurlstone.
Rachel gets sick and was engaged to Brunton the butler, he dumped her and she hated him. He was caught going through family documents and was fired. Brunton disappears the 3rd day of his last week of work. Then Rachel gets sick again and goes missing, all they could find was a linen bag of items in the lake.
Sherlock wanted to look at the Musgrave ritual. They go to the HUrlstone mansion to figure out how to solve the rituals riddle. Sherlock Holmes did the math to figure out where the entrance was for the ritual and it led to a cellar.
They found the spot and a chest with Bruntons dead body on it, in an underground cellar on the cellar floor.
They find out Brunton dies and that Rachel either killed him or on of the boards fell holding up the door causing Brunton to suffocate.
The treasure was the crown of Charles ||. Rachel was never heard from again.