Sherlock Holmes had opened his mouth to reply, when the door flew open, and Peterson, the commissionaire, rushed into the apartment with flushed cheeks and the face of a man who is dazed with astonishment.

"The goose, Mr. Holmes! The goose, sir!" he gasped.

"Eh? What of it, then? Has it returned to life and flapped off through the kitchen window?" Holmes twisted himself round upon the sofa to get a fairer view of the man's excited face.

"See here, sir! See what my wife found in its crop!" He held out his hand and displayed upon the centre of the palm a brilliantly scintillating blue stone, rather smaller than a bean in size, but of such purity and radiance that it twinkled like an electric point in the dark hollow of his hand.

Sherlock Holmes sat up with a whistle. "By Jove, Peterson!" said he, "this is treasure trove indeed. I suppose you know what you have got?"

"A diamond, sir? A precious stone. It cuts into glass as though it were putty."

"It's more than a precious stone. It is the precious stone."

"Not the Countess of Morcar's blue carbuncle!" I ejaculated.

"Precisely so. I ought to know its size and shape, seeing that I have read the advertisement about it in The Times every day lately. It is absolutely unique, and its value can only be conjectured, but the reward offered of 1000 pounds is certainly not within a twentieth part of the market price."

"A thousand pounds! Great Lord of mercy!" The commissionaire plumped down into a chair and stared from one to the other of us.

"That is the reward, and I have reason to know that there are sentimental considerations in the background which would induce the Countess to part with half her fortune if she could but recover the gem."

"It was lost, if I remember aright, at the Hotel Cosmopolitan," I remarked.

"Precisely so, on December 22nd, just five days ago. John Horner, a plumber, was accused of having abstracted it from the lady's jewel-case. The evidence against him was so strong that the case has been referred to the Assizes. I have some account of the matter here, I believe." He rummaged amid his newspapers, glancing over the dates, until at last he smoothed one out, doubled it over, and read the following paragraph: