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 uncarpeted stairs, and the sound of our movements echoing in hollow fashion around the deserted rooms.
Gaining the next floor, Harley, unable any longer to conceal his excitement, 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 Colonel Menendez,” he continued, “and the sheet of cardboard to represent his head, the hole which I have cut in it corresponds fairly nearly to the position of his forehead. Further assuming the bullet to have illustrated 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 is only 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 you come 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 the ash stick planted before it. I could see the piece of cardboard which surmounted it—and, through the hole cut in the cardboard, I could see the feeble flame of the candle nailed to the ninth yew tree!
