Summary
Alexander Holder, a banker, comes to Holmes to ask for help in locating the Beryl Coronet, a precious piece of jewelry that was entrusted to him by a member of the British high nobility as collateral for a loan. On a previous night, Holder woke up to find his son Arthur holding a broken portion of the coronet and so assumes the latter's guilt. However, Holmes doubts that Arthur was the culprit.
By examining Holder's house and its environs, and interviewing his niece Mary, Holmes discovers that it was in fact she who had, under the influence of her lover the notorious Sir George Burnwell, stolen the coronet. Holmes tracks down and confronts Burnwell and secures the return of the jewels, which he gives to Holder.
Analysis
This case is noteworthy for the complexity of the character relations that provide clues and red herrings for Holmes' deduction. Alexander Holder's strained relationship with his son Arthur, along with Arthur's association with Sir George Burnwell, seems to point towards Arthur as the thief; but in fact it is Mary who is totally under the control of Burnwell. Moreover, Mary points out, not falsely, that the family maid, Lucy, has been sneaking out of the house for rendezvouses with the local green grocer; this suggests their guilt but in fact serves as a parallel, albeit innocent, pair of lovers in conspiracy. By talking with Mary and Arthur, and by surveying the actual physical tracks left by the action of the crime, Holmes is able to untangle these complex associations and correctly identify the culprits. On the human side of this deduction is the amelioration of the first and central antagonistic relationship mentioned: between Holder father and son. In the same moment, the romance between Arthur and Mary is broken.
