"Yes, just that." The words came with quiet conviction.
"But I heard no other shot, and Philip Darwin was alive at eleven-thirty!"
"Of course you heard no shot. We're dealing with a clever man, I tell you, and he wasn't advertising his actions," returned McKelvie, with that note of impatience in his voice which crept into it whenever I failed immediately to grasp the point. "I'll show you how it was done, so that no one could possibly have heard that shot, even if there had been someone listening at door or windows, which, of course, there was not."
He walked to the safe, and unlocked the door. Then he inserted his key in the back wall and ushered me into the secret room.
"In here," he said, "no noise, however great, could be heard without these walls. They are sound-proof, for I have tested them myself. I fired a pistol by means of a mechanism, and then listened in the hall for its explosion. I heard nothing. When I returned to this room the pistol had gone off, as was intended. So you can see that shooting his victim in here with the doors closed there was no chance that the shot would be heard by anyone in the house at the time."
I stared at him in astonishment. "But, McKelvie, Jones proved beyond the shadow of a doubt that Philip Darwin had just risen in his chair at the table when he was shot," I protested.
"Jones proved it!" he jeered. "Ye gods! Jones proved it! Of course he proved it. What else would you expect of Jones? Why do you suppose the murderer took the trouble to make those marks in the carpet except to fool the police?" he raged. "Certainly Jones proved it when it was put there for that purpose!"
"Granted," I said pacifically. "He shot Darwin in this secret room. Then what?"
McKelvie calmed down and resumed his story. "Then he proceeded to manufacture evidence. He carried his victim through the safe," returning to the study as he spoke and relocking the entrance, "placed him in that chair and arranged everything to look as though Philip Darwin had been writing, as indeed he had been when Orton came in at eleven-thirty. Then, satisfied that all was as perfect as he could make it, he turned off the light and waited."
"What for?"