In the story, chance brings a battered hat and a Christmas goose to Holmes. When a stolen gem known as the blue carbuncle is found in the goose’s gullet, Holmes and Watson set out to discover the sequence of events that took the stone from a countess’ jewel case to Baker Street.
"The Adventure of the Blue Carbuncle" has been adapted for television and radio many times. The most faithful television adaptation of the story to date is the 1984 episode of The Adventures of Sherlock Holmes Granada series starring Jeremy Brett.
The story was ranked third, behind only "The Adventure of the Speckled Band" and "The Red-Headed League," in the "Ten Best Contest" held by the leading Sherlockian publication The Baker Street Journal in 1959.
On the second morning after Christmas, Dr. Watson visits Sherlock Holmes and finds him lounging next to a battered bowler hat. Holmes explains that Peterson, the commissionaire, brought it on Christmas morning. Peterson had rushed over to assist a man being assailed by some ruffians early that morning, but the man ran away leaving behind the hat and a Christmas goose he had been carrying. The goose was tagged "For Mrs. Henry Baker" and the hat bears the initials "H. B."
No advertisement appeared for the lost items in the papers, so Peterson took the goose before it spoiled while Holmes kept the hat for his amusement. He has deduced much information about its owner from the hat including his age, financial situation, and domestic problems. As Holmes explains his inferences, Watson laughs and comments that, while ingenious, the exercise seems a waste of energy without any crime involved.
Just then Peterson rushes in to show them what his wife found in the goose's crop; a brilliant blue gem. Holmes identifies it as the blue carbuncle stolen from the Countess of Morcar's hotel room five days ago. A plumber with a previous robbery conviction named John Horner has been arrested on evidence from James Ryder, head attendant. Ryder had found the bureau forced open and jewel case lying empty after Horner did repair work in the room. The Countess' maid gave collaborating evidence.
Given the new development, Holmes asks Peterson to put an advertisement in papers for Henry Baker and to pick up a replacement goose on his way back. When Baker appears at the appointed time, he turns out to be just as Holmes described. Baker is delighted with the fresh goose and shows no interest in the feathers, legs, and crop from the original bird. Holmes asks where he bought the goose, and Baker replies that it came from the Alpha Inn. The landlord had run a "goose club" for his patrons to deposit a few pence weekly towards a bird at Christmas.
At the Alpha Inn, Holmes and Watson learn that the geese came from a salesman named Breckinridge. They proceed to the market where they find Breckinridge at his stall. When they inquire about the geese, the man becomes angry and refuses to say where the birds came from. He had already been pestered about the same birds earlier. Holmes shrugs it off and says it was just for a bet he had on the goose being country-bred. When Breckinridge says it was town-bred, Holmes refuses to believe him and bets a sovereign against him. The salesman, pleased to prove Holmes wrong, brings out his books which show the birds' supplier, a Mrs. Oakshott in town. Holmes throws down the sovereign in apparent disgust. Once they are away, he has a good laugh, having correctly judged Breckinridge as a betting man and skillfully drawn out the information.
As they discuss plans to visit Mrs. Oakshott, Holmes and Watson hear a commotion from the stall and witness Breckinridge chase away a small man looking for the geese. They catch up with the man and Holmes tells him he knows all about the geese sold by Mrs. Oakshott. He demands a name before discussing business, however, so the desperate man reluctantly identifies himself as James Ryder.
They take Ryder back to Baker Street where Holmes confronts him about the gem. After nearly fainting, the frightened man admits the maid had told him about the stone. Holmes knows it was Ryder who sent for Horner, aware of his robbery record, in order to pin the crime on him. Ryder breaks down and begs for mercy, swearing he never went wrong before, will never do so again, and will leave the country so the charge against Horner would break down. Holmes asks him how the stone got into the goose and the goose into the open market, and Ryder tells his story.
As soon as Horner was arrested, he made for the home of his sister, Mrs. Oakshott. He was afraid of being searched, and needed a way to safely take the stone to Kilburn to consult a friend about selling it. He got an idea upon seeing the geese and, remembering his sister had promised him one for Christmas, he grabbed a big one with a barred tail. As he forced the stone down its throat, the bird struggled and got away, mixing back into the flock. With his sister’s blessing, he took the goose to Kilburn only to find no stone inside. He rushed back and learned there had been two that looked alike, but by then the geese had been sold. He went to Breckinridge but he had already sold the lot and would not tell him anything.
Ryder bursts into tears. Holmes sits contemplating for some time before rising to throw open the door. He tells Ryder to get out, and the man rushes out. Holmes assures Watson afterwards that Horner is in no danger without Ryder to appear against him, and that Ryder is too frightened to go wrong again. He then remarks "Besides, it is the season of forgiveness."
- Sound file of public domain audiobook of "The Adventure of the Blue Carbuncle" from LibriVox
- Another Sherlock Holmes mystery involving a jewel stolen from a hotel room; "The Adventure of the Six Napoleons."
- ↑ A carbuncle is a red gem, usually a garnet, cut en cabochon (un-faceted). Since there are no blue garnets, some speculate the "blue carbuncle" was actually a blue diamond, while others suggest a star sapphire.
- ↑ One pound gold coin, equivalent to perhaps a $100 bet today.