He had recovered his self-possession in an instant. “I was staggered for the moment,” he said, “but the thing is quite natural. My memory failed me, or I should have been able to foretell it. There is nothing more to be learned here. Let us go down.”

“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 a touch of impatience. “You know my methods. Apply them, and it will be instructive to compare results.”

“I cannot conceive anything which will cover the facts,” I answered.

“It will be clear enough to you soon,” he said, in an off-hand way. “I think that there is nothing else of importance here, but I will look.” He whipped out his lens and a tape measure, and hurried about the room on his knees, measuring, comparing, examining, with his long thin nose only a few inches from the planks, and his beady eyes gleaming and deep-set like those of a bird. So swift, silent, and furtive were his movements, like those of a trained blood-hound picking out a scent, that I could not but think what a terrible criminal he would have made had he turned his energy and sagacity against the law, instead of exerting them in its defence. As he hunted about, he kept muttering to himself, and finally he broke out into a loud crow of delight.

“We are certainly in luck,” said he. “We ought to have very little trouble now. Number One has had the misfortune to tread in the creosote. You can see the outline of the edge of his small foot here at the side of this evil-smelling mess. The carboy has been cracked, You see, and the stuff has leaked out.”

“What then?” I asked.

“Why, we have got him, that’s all,” said he. “I know a dog that would follow that scent to the world’s end. If a pack can track a trailed herring across a shire, how far can a specially-trained hound follow so pungent a smell as this? It sounds like a sum in the rule of three. The answer should give us the—But halloa! here are the accredited representatives of the law.”

Heavy steps and the clamour of loud voices were audible from below, and the hall door shut with a loud crash.

“Before they come,” said Holmes, “just put your hand here on this poor fellow’s arm, and here on his leg. What do you feel?”

“The muscles are as hard as a board,” I answered.

“Quite so. They are in a state of extreme contraction, far exceeding the usual rigor mortis. Coupled with this distortion of the face, this Hippocratic smile, or ‘risus sardonicus,’ as the old writers called it, what conclusion would it suggest to your mind?”