“Before this avenger got away, Barker and the wife had reached the room. The assassin convinced them that any attempt to arrest him would lead to the publication of some hideous scandal. They were converted to this idea, and preferred to let him go. For this purpose they probably lowered the bridge, which can be done quite noiselessly, and then raised it again. He made his escape, and for some reason thought that he could do so more safely on foot than on the bicycle. He therefore left his machine where it would not be discovered until he had got safely away. So far we are within the bounds of possibility, are we not?”

“Well, it is possible, no doubt,” said I, with some reserve.

“We have to remember, Watson, that whatever occurred is certainly something very extraordinary. Well, now, to continue our supposititious case, the couple — not necessarily a guilty couple — realize after the murderer is gone that they have placed themselves in a position in which it may be difficult for them to prove that they did not themselves either do the deed or connive at it. They rapidly and rather clumsily met the situation. The mark was put by Barker’s bloodstained slipper upon upon the windowsill to suggest how the fugitive got away. They obviously were the two who must have heard the sound of the gun; so they gave the alarm exactly as they would have done, but a good half hour after the event.”

“And how do you propose to prove all this?”

“Well, if there were an outsider, he may be traced and taken. That would be the most effective of all proofs. But if not — well, the resources of science are far from being exhausted. I think that an evening alone in that study would help me much.”

“An evening alone!”

“I propose to go up there presently. I have arranged it with the estimable Ames, who is by no means whole-hearted about Barker. I shall sit in that room and see if its atmosphere brings me inspiration. I’m a believer in the genius loci. You smile, Friend Watson. Well, we shall see. By the way, you have that big umbrella of yours, have you not?”

“It is here.”

“Well, I’ll borrow that if I may.”

“Certainly — but what a wretched weapon! If there is danger —”

“Nothing serious, my dear Watson, or I should certainly ask for your assistance. But I’ll take the umbrella. At present I am only awaiting the return of our colleagues from Tunbridge Wells, where they are at present engaged in trying for a likely owner to the bicycle.”

It was nightfall before Inspector MacDonald and White Mason came back from their expedition, and they arrived exultant, reporting a great advance in our investigation.

“Man, I’ll admeet that I had my doubts if there was ever an outsider,” said MacDonald, “but that’s all past now. We’ve had the bicycle identified, and we have a description of our man; so that’s a long step on our journey.”

I did not pause to argue over this atrocious sentiment.

“I shall be back in an hour or two,” I remarked.

“All right! Good luck! But, I say, if you are crossing the river you may as well return Toby, for I don’t think it is at all likely that we shall have any use for him now.”

I took our mongrel accordingly and left him, together with a half-sovereign, at the old naturalist’s in Pinchin Lane. At Camberwell I found Miss Morstan a little weary after her night’s adventures but very eager to hear the news. Mrs. Forrester, too, was full of curiosity. I told them all that we had done, suppressing, however, the more dreadful parts of the tragedy. Thus although I spoke of Mr. Sholto’s death, I said nothing of the exact manner and method of it. With all my omissions, however, there was enough to startle and amaze them.

“It is a romance!” cried Mrs. Forrester. “An injured lady, half a million in treasure, a black cannibal, and a wooden-legged ruffian. They take the place of the conventional dragon or wicked earl.”

“And two knight-errants to the rescue,” added Miss Morstan with a bright glance at me.

“Why, Mary, your fortune depends upon the issue of this search. I don’t think that you are nearly excited enough. Just imagine what it must be to be so rich and to have the world at your feet!”

It sent a little thrill of joy to my heart to notice that she showed no sign of elation at the prospect. On the contrary, she gave a toss of her proud head, as though the matter were one in which she took small interest.

“It is for Mr. Thaddeus Sholto that I am anxious,” she said. “Nothing else is of any consequence; but I think that he has behaved most kindly and honourably throughout. It is our duty to clear him of this dreadful and unfounded charge.”

It was evening before I left Camberwell, and quite dark by the time I reached home. My companion’s book and pipe lay by his chair, but he had disappeared. I looked about in the hope of seeing a note, but there was none.

“I suppose that Mr. Sherlock Holmes has gone out,” I said to Mrs. Hudson as she came up to lower the blinds.

“No, sir. He has gone to his room, sir. Do you know, sir,” sinking her voice into an impressive whisper, “I am afraid for his health.”

“Why so, Mrs. Hudson?”

“Well, he’s that strange, sir. After you was gone he walked and he walked, up and down, and up and down, until I was weary of the sound of his footstep. Then I heard him talking to himself and muttering, and every time the bell rang out he came on the stairhead, with ‘What is that, Mrs. Hudson?’ And now he has slammed off to his room, but I can hear him walking away the same as ever. I hope he’s not going to be ill, sir. I ventured to say something to him about cooling medicine, but he turned on me, sir, with such a look that I don’t know how ever I got out of the room.”