The Blue Carbuncle is a large, extremely valuable gemstone owned by the Countess of Morcar. To her horror she finds that it has been stolen. To Sherlock Holmes's surprise he finds himself in possession of it, via a Christmas goose. Tracing the previous owners of the goose Holmes sets out to find out who stole the Blue Carbuncle.
A wonderful Christmas episode of Sherlock Holmes, one of the best, if not THE best, episodes of the show. There's a very interesting mystery, solved by tracing the path of a goose. The perpetrator is a bit obvious but in the grand scheme of things this is a minor negative.
Moreover, there is a great Christmas "vibe" to proceedings, making it a great episode to watch at that time of the year. Even rational, curmudgeonly Holmes gets into the spirit of things. On that note, we do see a more friendly, common man representation of Holmes in this episode and it is very refreshing.