“Exactly. I fancy the yew alley, though not marked under that name, must stretch along this line, with the moor, as you perceive, upon the right of it. This small clump of buildings here is the hamlet of Grimpen, where our friend Dr. Mortimer has his headquarters. Within a radius of five miles there are, as you see, only a very few scattered dwellings. Here is Lafter Hall, which was mentioned in the narrative. There is a house indicated here which may be the residence of the naturalist—Stapleton, if I remember right, was his name. Here are two moorland farmhouses, High Tor and Foulmire. Then fourteen miles away the great convict prison of Princetown. Between and around these scattered points extends the desolate, lifeless moor. This, then, is the stage upon which tragedy has been played, and upon which we may help to play it again.”

“It must be a wild place.”

“Yes, the setting is a worthy one. If the devil did desire to have a hand in the affairs of men—”

“Then you are yourself inclining to the supernatural explanation.”

“The devil’s agents may be of flesh and blood, may they not? There are two questions waiting for us at the outset. The one is whether any crime has been committed at all; the second is, what is the crime and how was it committed? Of course, if Dr. Mortimer’s surmise should be correct, and we are dealing with forces outside the ordinary laws of Nature, there is an end of our investigation. But we are bound to exhaust all other hypotheses before falling back upon this one. I think we’ll shut that window again, if you don’t mind. It is a singular thing, but I find that a concentrated atmosphere helps a concentration of thought. I have not pushed it to the length of getting into a box to think, but that is the logical outcome of my convictions. Have you turned the case over in your mind?”

“Yes, I have thought a good deal of it in the course of the day.”

“What do you make of it?”

“It is very bewildering.”

“It has certainly a character of its own. There are points of distinction about it. That change in the footprints, for example. What do you make of that?”

“Mortimer said that the man had walked on tiptoe down that portion of the alley.”

“He only repeated what some fool had said at the inquest. Why should a man walk on tiptoe down the alley?”

“What then?”

“He was running, Watson—running desperately, running for his life, running until he burst his heart—and fell dead upon his face.”

“Running from what?”

“There lies our problem. There are indications that the man was crazed with fear before ever he began to run.”

“How can you say that?”