Up to the very moment that Paul Harley, who had withdrawn, rejoined usin the garden, Inspector Aylesbury had not grasped the significance ofthat candle burning upon the yew tree. He continued to stare at it asif hypnotized, and when my friend re-appeared, carrying a long ash staffand a sheet of cardboard, I could have laughed to witness the expressionupon the Inspector's face, had I not been too deeply impressed with thatwhich underlay this strange business.
Wessex, on the other hand, was watching my friend eagerly, as an earneststudent in the class-room might watch a demonstration by some celebratedlecturer.
"You will notice," said Paul Harley, "that I have had a number of boardslaid down upon the ground yonder, near the sun-dial. They cover a spotwhere the turf has worn very thin. Now, this garden, because of itssunken position, is naturally damp. Perhaps, Wessex, you would take upthese planks for me."
Inspector Wessex obeyed, and Harley, laying the ash stick and cardboardupon the ground, directed the ray of an electric torch upon the spotuncovered.
"The footprints of Colonel Menendez!" he explained. "Here he turnedfrom the tiled path. He advanced three paces in the direction of thesun-dial, you observe, then stood still, facing we may suppose, sincethis is the indication of the prints, in a southerly direction."
"Straight toward the Guest House," muttered Inspector Aylesbury.
"Roughly," corrected Harley. "He was fronting in that direction,certainly, but his head may have been turned either to the right or tothe left. You observe from the great depth of the toe-marks that onthis spot he actually fell. Then, here"--he moved the light--"is theimpression of his knee, and here again--"
He shone the white ray upon a discoloured patch of grass, and thenreturned the lamp to his pocket.
"I am going to make a hole in the turf," he continued, "directly betweenthese two footprints, which seem to indicate that the Colonel wasstanding in the military position of attention at the moment that he methis death."
With the end of the ash stick, which was pointed, he proceeded to dothis.
"Colonel Menendez," he went on, "stood rather over six feet in hisshoes. The stick which now stands upright in the turf measures six feet,from the chalk mark up to which I have buried it to the slot which Ihave cut in the top. Into this slot I now wedge my sheet of cardboard."
As he placed the sheet of cardboard in the slot which he had indicated,I saw that a round hole was cut in it some six inches in diameter. Wewatched these proceedings in silence, then:
"If you will allow me to adjust the candle, gentlemen," said Harley,"which has burned a little too low for my purpose, I shall proceed tothe second part of this experiment."
He walked up to the yew tree, and by means of bending the nail upwardhe raised the flame of the candle level with the base of the embeddedbullet.
"By heavens!" cried Wessex, suddenly divining the object of theseproceedings, "Mr. Harley, this is genius!"
"Thank you, Wessex," Harley replied, quietly, but nevertheless he wasunable to hide his gratification. "You see my point?"
"Certainly."
"In ten minutes we shall know the truth."
"Oh, I see," muttered Inspector Aylesbury; "we shall know the truth, eh?If you ask me the truth, it's this, that we are a set of lunatics."
"My dear Inspector Aylesbury," said Harley, good humouredly, "surely youhave grasped the lesson of experiment number one?"
"Well," admitted the other, "it's funny, certainly. I mean, it wants alot of explaining, but I can't say I'm convinced."
"That's a pity," murmured Wessex, "because I am."
"You see, Inspector," Harley continued, patiently, "the body of ColonelMenendez as it lay formed a straight line between the sun-dial and thehut in the garden of the Guest House. That is to say: a line drawn fromthe window of the hut to the sun-dial must have passed through the body.Very well. Such an imaginary line, if continued _beyond_ the sun-dial,would have terminated near the base of the _seventh yew_ tree.Accordingly, I naturally looked for the _bullet_ there. It was notthere. But I found it, as you know, in the ninth tree. Therefore, theshot could not possibly have been fired from the Guest House, becausethe spot in the ninth yew where the bullet had lodged is not visiblefrom the Guest House."
Inspector Aylesbury removed his cap and scratched his head vigorously.
"In order that we may avoid waste of valuable time," said Harley,finally, "let us take a hasty observation from here. As a matterof fact, I have done so already, as nearly as was possible, withoutemploying this rough apparatus."
He knelt down beside the yew tree, lowering his head so that thecandlelight shone upon the brown, eager face, and looked upward, overthe top of the sun-dial and through the hole in the cardboard.
"Yes," he muttered, a note of rising excitement in his voice. "As Ithought, as I thought. Come, gentlemen, let us hurry."
He walked rapidly out of the garden, and up the steps, whilst wefollowed dumb with wonder--or such at any rate was the cause of my ownsilence.
In the hall Pedro was standing, a bunch of keys in his hand, andevidently expecting Harley.
"Will you take us by the shortest way to the tower stairs?" my frienddirected.
"Yes, sir."
Doubting, wondering, scarcely knowing whether to be fearful or jubilant,I followed, along a carpeted corridor, and thence, a heavy, oakendoor being unlocked, across a dusty and deserted apartment apparentlyintended for a drawing room. From this, through a second doorway wewere led into a small, square, unfurnished room, which I knew must besituated in the base of the tower. Yet a third door was unlocked, and:
"Here is the stair, sir," said Pedro.
In Indian file we mounted to the first floor, to find ourselves in asecond, identical room, also stripped of furniture and decorations.Harley barely glanced out of the northern window, shook his head, and:
"Next floor, Pedro," he directed.
Up we went, our footsteps arousing a cloud of dust from the uncarpetedstairs, and the sound of our movements echoing in hollow fashion aroundthe deserted rooms.
Gaining the next floor, Harley, unable any longer to conceal hisexcitement, ran to the north window, looked out, and:
"Gentlemen," he said, "my experiment is complete!"
He turned, his back to the window, and faced us in the dusk of the room.
"Assuming the ash stick to represent the upright body of ColonelMenendez," he continued, "and the sheet of cardboard to represent hishead, the hole which I have cut in it corresponds fairly nearly tothe position of his forehead. Further assuming the bullet to haveillustrated Euclid's definition of a straight line, such a line,_followed back_ from the yew tree to the spot where the rifle rested,would pass through the hole in the cardboard! In other words, there isonly one place from which it is possible to see the flame of the candle_through the hole in the cardboard_: the place where the rifle rested!Stand here in the left-hand angle of the window and stoop down! Will youcome first, Knox?"
I stepped across the room, bent down, and stared out of the window,across the Tudor garden. Plainly I could see the sun-dial with theash stick planted before it. I could see the piece of cardboard whichsurmounted it--and, through the hole cut in the cardboard, I could seethe feeble flame of the candle nailed to the ninth yew tree!
I stood upright, knowing that I had grown pale, and conscious of a moistsensation upon my forehead.
"Merciful God!" I said in a hollow voice. "It was from _this window_that the shot was fired which killed him!"
CHAPTER XXXIV
THE CREEPING SICKNESS