“There remained the third possibility, into which, rare and unlikely as it was, everything seemed to fit. Leprosy is not uncommon in South Africa. By some extraordinary chance this youth might have contracted it. His people would be placed in a very dreadful position, since they would desire to save him from segregation. Great secrecy would be needed to prevent rumours from getting about and subsequent interference by the authorities. A devoted medical man, if sufficiently paid, would easily be found to take charge of the sufferer. There would be no reason why the latter should not be allowed freedom after dark. Bleaching of the skin is a common result of the disease. The case was a strong one — so strong that I determined to act as if it were actually proved. When on arriving here I noticed that Ralph, who carries out the meals, had gloves which are impregnated with disinfectants, my last doubts were removed. A single word showed you, sir, that your secret was discovered, and if I wrote rather than said it, it was to prove to you that my discretion was to be trusted.”

I was finishing this little analysis of the case when the door was opened and the austere figure of the great dermatologist was ushered in. But for once his sphinx-like features had relaxed and there was a warm humanity in his eyes. He strode up to Colonel Emsworth and shook him by the hand.

“It is often my lot to bring ill-tidings and seldom good,” said he. “This occasion is the more welcome. It is not leprosy.”

“What?”

“A well-marked case of pseudo-leprosy or ichthyosis, a scalelike affection of the skin, unsightly, obstinate, but possibly curable, and certainly noninfective. Yes, Mr. Holmes, the coincidence is a remarkable one. But is it coincidence? Are there not subtle forces at work of which we know little? Are we assured that the apprehension from which this young man has no doubt suffered terribly since his exposure to its contagion may not produce a physical effect which simulates that which it fears? At any rate, I pledge my professional reputation — But the lady has fainted! I think that Mr. Kent had better be with her until she recovers from this joyous shock.”

It was pleasant to Dr. Watson to find himself once more in the untidy room of the first floor in Baker Street which had been the starting-point of so many remarkable adventures. He looked round him at the scientific charts upon the wall, the acid-charred bench of chemicals, the violin-case leaning in the corner, the coal-scuttle, which contained of old the pipes and tobacco. Finally, his eyes came round to the fresh and smiling face of Billy, the young but very wise and tactful page, who had helped a little to fill up the gap of loneliness and isolation which surrounded the saturnine figure of the great detective.

“It all seems very unchanged, Billy. You don’t change, either. I hope the same can be said of him?”

Billy glanced with some solicitude at the closed door of the bedroom.