“Surely，” said he with something of the air of a clinical professorexpounding to his class. “Just sit in the corner there， that yourfootprints may not complicate matters. Now to work！ In the firstplace， how did these folk come and how did they go？ The doorhas not been opened since last night. How of the window？” Hecarried the lamp across to it， muttering his observations aloud thewhile but addressing them to himself rather than to me. “Windowis snibbed on the inner side. Frame-work is solid. No hinges atthe side. Let us open it. No water-pipe near. Roof quite out ofreach. Yet a man has mounted by the window. It rained a little lastnight. Here is the print of a foot in mould upon the sill. And hereis a circular muddy mark， and here again upon the floor， and hereagain by the table. See here， Watson！ This is really a very prettydemonstration.”
I looked at the round， well-defined muddy discs.
“This is not a foot-mark，” said I.
“It is something much more valuable to us. It is the impressionof a wooden stump. You see here on the sill is the boot-mark， aheavy boot with a broad metal heel， and beside it is the mark ofthe timber-toe.”
“It is the wooden-legged man.”
“Quite so. But there has been some one else—a very able andefficient ally. Could you scale that wall， doctor？”
I looked out of the open window. The moon still shone brightlyon that angle of the house. We were a good sixty feet from theround， and， look where I would， I could see no foothold， nor asmuch as a crevice in the brickwork.
“It is absolutely impossible，” I answered.
“Without aid it is so. But suppose you had a friend up herewho lowered you this good stout rope which I see in the corner，securing one end of it to this great hook in the wall. Then， I think，if you were an active man， You might swarm up， wooden leg andall. You would depart， of course， in the same fashion， and your allywould draw up the rope， untie it from the hook， shut the window，snib it on the inside， and get away in the way that he originallycame. As a minor point， it may be noted，” he continued， fingeringthe rope， “that our wooden-legged friend， though a fair climber，was not a professional sailor. His hands were far from horny. Mylens discloses more than one blood-mark， especially towards theend of the rope， from which I gather that he slipped down withsuch velocity that he took the skin off his hand.”
“This is all very well，” said I； “but the thing becomes moreunintelligible than ever. How about this mysterious ally？ Howcame he into the room？”
“Yes， the ally！” repeated Holmes pensively. “There are featuresof interest about this ally. He lifts the case from the regions of thecommonplace. I fancy that this ally breaks fresh ground in the annalsof crime in this country—though parallel cases suggest themselvesfrom India and， if my memory serves me， from Senegambia.”
“How came he， then？” I reiterated. “The door is locked； thewindow is inaccessible. Was it through the chimney？”
“The grate is much too small，” he answered. “I had alreadyconsidered that possibility.”
“How， then？” I persisted.
“You will not apply my precept，” he said， shaking his head.
“How often have I said to you that when you have eliminated theimpossible， whatever remains， HOWEVER IMPROBABLE， mustbe the truth？ We know that he did not come through the door，the window， or the chimney. We also know that he could not havebeen concealed in the room， as there is no concealment possible.
When， then， did he come？”
“He came through the hole in the roof！” I cried.
“Of course he did. He must have done so. If you will havethe kindness to hold the lamp for me， we shall now extend ourresearches to the room above—the secret room in which thetreasure was found.”
He mounted the steps， and， seizing a rafter with either hand，he swung himself up into the garret. Then， lying on his face， hereached down for the lamp and held it while I followed him.
The chamber in which we found ourselves was about ten feetone way and six the other. The floor was formed by the rafters，with thin lath and plaster between， so that in walking one hadto step from beam to beam. The roof ran up to an apex and wasevidently the inner shell of the true roof of the house. There wasno furniture of any sort， and the accumulated dust of years laythick upon the floor.
“Here you are， you see，” said Sherlock Holmes， putting his handagainst the sloping wall. “This is a trapdoor which leads out on tothe roof. I can press it back， and here is the roof itself， sloping at agentle angle. This， then， is the way by which Number One entered.
Let us see if we can find any other traces of his individuality？”
He held down the lamp to the floor， and as he did so I saw forthe second time that night a startled， surprised look come over hisface. For myself， as I followed his gaze， my skin was cold under myclothes. The floor was covered thickly with the prints of a nakedfoot—clear， well-defined， perfectly formed， but scarce half the sizeof those of an ordinary man.
“Holmes，” I said in a whisper， “a child has done this horrid thing.”
He had recovered his self-possession in an instant.
“I was staggered for the moment，” he said， “but the thing isquite natural. My memory failed me， or I should have been ableto foretell it. There is nothing more to be learned here. Let us godown.”
“What is your theory， then， as to those footmarks？” I asked，eagerly when we had regained the lower room once more.
“My dear Watson， try a little analysis yourself，” said he with atouch of impatience. “You know my methods. Apply them， and itwill be instructive to compare results.”
“I cannot conceive anything which will cover the facts，” Ianswered.
“It will be clear enough to you soon，” he said， in an offhand way. “Ithink that there is nothing else of importance here， but I will look.”