Allen did not start out to inquire for the slamming door. Why didyour guilty couple do all this， Watson？”
“I confess that I can’t explain it.”
“Then again， if a woman and her lover conspire to murder ahusband， are they going to advertise their guilt by ostentatiouslyremoving his wedding ring after his death？ Does that strike you asvery probable， Watson？”
“No， it does not.”
“And once again， if the thought of leaving a bicycle concealedoutside had occurred to you， would it really have seemed worthdoing when the dullest detective would naturally say this is anobvious blind， as the bicycle is the first thing which the fugitiveneeded in order to make his escape.”
“I can conceive of no explanation.”
“And yet there should be no combination of events for whichthe wit of man cannot conceive an explanation. Simply as a mentalexercise， without any assertion that it is true， let me indicate apossible line of thought. It is， I admit， mere imagination； but howoften is imagination the mother of truth？
“We will suppose that there was a guilty secret， a really shamefulsecret in the life of this man Douglas. This leads to his murderby someone who is， we will suppose， an avenger， someone fromoutside. This avenger， for some reason which I confess I am still ata loss to explain， took the dead man’s wedding ring. The vendettamight conceivably date back to the man’s first marriage， and thering be taken for some such reason.
“Before this avenger got away， Barker and the wife had reachedthe room. The assassin convinced them that any attempt to arresthim would lead to the publication of some hideous scandal. Theywere converted to this idea， and preferred to let him go. For thispurpose they probably lowered the bridge， which can be donequite noiselessly， and then raised it again. He made his escape， andfor some reason thought that he could do so more safely on footthan on the bicycle. He therefore left his machine where it wouldnot be discovered until he had got safely away. So far we are withinthe 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 iscertainly something very extraordinary. Well， now， to continue oursupposititious case， the couple—not necessarily a guilty couple—realize after the murderer is gone that they have placed themselvesin a position in which it may be difficult for them to prove thatthey did not themselves either do the deed or connive at it. Theyrapidly and rather clumsily met the situation. The mark was putby Barker’s bloodstained slipper upon the window-sill to suggesthow the fugitive got away. They obviously were the two who musthave heard the sound of the gun； so they gave the alarm exactly asthey 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 thatan evening alone in that study would help me much.”
“An evening alone！”
“I propose to go up there presently. I have arranged it withthe estimable Ames， who is by no means wholehearted aboutBarker. I shall sit in that room and see if its atmosphere bringsme inspiration. I’m a believer in the genius loci. You smile， FriendWatson. Well， we shall see. By the way， you have that big umbrellaof 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 foryour assistance. But I’ll take the umbrella. At present I am onlyawaiting the return of our colleagues from Tunbridge Wells， wherethey are at present engaged in trying for a likely owner to thebicycle.”
It was nightfall before Inspector MacDonald and White Masoncame 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 anoutsider，” said MacDonald， “but that’s all past now. We’ve had thebicycle identified， and we have a description of our man； so that’sa long step on our journey.”
“It sounds to me like the beginning of the end，” said Holmes.
“I’m sure I congratulate you both with all my heart.”
“Well， I started from the fact that Mr. Douglas had seemeddisturbed since the day before， when he had been at TunbridgeWells. It was at Tunbridge Wells then that he had becomeconscious of some danger. It was clear， therefore， that if a manhad come over with a bicycle it was from Tunbridge Wells thathe might be expected to have come. We took the bicycle overwith us and showed it at the hotels. It was identified at once bythe manager of the Eagle Commercial as belonging to a mannamed Hargrave， who had taken a room there two days before.
This bicycle and a small valise were his whole belongings. Hehad registered his name as coming from London， but had givenno address. The valise was London made， and the contents wereBritish； but the man himself was undoubtedly an American.”
“Well， well，” said Holmes gleefully， “you have indeed done somesolid work while I have been sitting spinning theories with myfriend！ It’s a lesson in being practical， Mr. Mac.”
“Ay， it’s just that， Mr. Holmes，” said the inspector withsatisfaction.
“But this may all fit in with your theories，” I remarked.
“That may or may not be. But let us hear the end， Mr. Mac. Wasthere nothing to identify this man？”
“So little that it was evident that he had carefully guardedhimself against identification. There were no papers or letters， andno marking upon the clothes. A cycle map of the county lay onhis bedroom table. He had left the hotel after breakfast yesterdaymorning on his bicycle， and no more was heard of him until ourinquiries.”
“That’s what puzzles me， Mr. Holmes，” said White Mason.