ADVENTURE OF THE BERYL CORONET by Sir Arthur Conan Doyle

A banker, Mr. Alexander Holder makes a loan of £50,000 to a socially prominent client, who leaves the Beryl Coronet - one of the most valuable public possessions in existence - as security. Holder feels that he must not leave this rare and precious piece of jewelry in his personal safe at the bank, and so he takes it home with him to lock it up there. He is awoken in the night by a noise, enters his dressing room, and is horrified to see his son Arthur with the coronet in his hands. Three beryls are missing from it, and the coronet itself is already broken. In a panic, Holder travels to see Holmes, who agrees to take the case.
As Holmes was starting to handle the case, some peculiarities appeared. Arthur is refusing to give a statement of any kind. Holmes then found that even a strong man like him could not break the coronet without making any noise. Holmes begins to believe that Arthur didn't take the beryls. Someone else must have done it. Holmes totally realizes that the failure to resolve the case will result in Mr. Holder's dishonor, and will become a national scandal.
Holmes sets about not only reviewing the details that he learns from Holder, but also examining the footprints in the snow outside. Eventually, Holmes solves the mystery, and Holder is flabbergasted to find that his niece Mary was in league with a notorious criminal, Sir George Burnwell, although she is unaware of his character. The two of them escape justice; however, Holmes is convinced that they will receive their punishment in due time.

First published in the Strand Magazine, May 1892, with 9 illustrations by Sidney Paget.