"The Adventure of the Beryl Coronet", one of the 56 short Sherlock Holmes stories written by British author Sir Arthur Conan Doyle, is the eleventh of the twelve stories collected in The Adventures of Sherlock Holmes. The story was first published in Strand Magazine in May 1892.
A banker, Mr. Alexander Holder of Streatham, makes a loan of £50,000 to a socially prominent client, who leaves a beryl coronet - one of the most valuable public possessions in existence - as collateral. Holder feels that he must not leave this rare and precious piece of jewellery in his personal safe at the bank, and so he takes it home with him to lock it up there. He is awakened in the night by a noise, enters his dressing room, and is horrified to see his son Arthur with the coronet in his hands, apparently trying to bend it. Holder's niece Mary comes at the sound of all the shouting and, seeing the damaged coronet, faints dead away. Three beryls are missing from it. In a panic, Mr. Holder travels to see Holmes, who agrees to take the case.