The Blue Carbuncle

This story takes place almost entirely against Christmas. Watson visits his friend Holmes, who examines an old hat (deductively identifying its owner) brought to him by Commissioner Peterson, and a Christmas goose that someone lost during a fight with street cutthroats.
Later, a blue carbuncle - a rare precious ruby - was found in the goose's throat.
Holmes cannot resist such a unique mystery, and he and Watson begin to walk through various corners of Lorndon to discover how exactly the stolen jewel ended up in the goose's throat.
Translated by Mykola Dmytrenko.