Summary: Watson visits Holmes at Christmas time and finds him contemplating a battered old hat, brought to him by the commissionaire Peterson after it and a Christmas goose had been dropped by a man in a scuffle with some street ruffians. Peterson takes the goose home to eat it, but comes back later with a precious blue carbuncle. His wife had found it in the bird's crop. Holmes cannot resist a good mystery, and he and Watson set out across the city to determine exactly how the stolen jewel wound up in a goose's crop.
