In "The Adventure of the Beryl Coronet", a banker, Mr. Alexander Holder, 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. Feeling that he must not leave this rare and precious piece of jewelry in his personal safe at the bank, he takes it home with him.
Awakened by a noise in the night, he is horrified to see his son playing with the coronet and apparently trying to bend it. Three beryls are now missing from it. In a panic, Mr. Holder travels to see Holmes, who agrees to take the case.