Orton blanched like the coward that he was. "But—but, I'm innocent," he said, indignantly.
"Well, you wouldn't be the first innocent person to grace a cell, I assure you," retorted McKelvie dryly. "You have told us everything?"
"Yes, everything."
"Very well, then you can answer several questions. You are positive you heard the key turned in the study door when you stood in the hall at ten minutes to twelve?" continued McKelvie. "Remember I want facts, and not impressions."
"I am as positive as that I am sitting here. But it was more toward five minutes to twelve because I paused to ascertain if Mrs. Darwin was still in the drawing-room and I listened for a minute or two before I started for the dining-room," replied Orton with conviction.
"A minute is a good long while, longer than you think, Orton," returned McKelvie. "But that point is, after all, immaterial. We will say that somewhere between ten and five minutes to twelve the study door was unlocked from the inside," and he looked at me significantly.
If he was right in his premise, then the person who unlocked that door could have been none other than the criminal, for at ten minutes before midnight Philip Darwin was past unlocking doors! Yet it seemed a foolhardy thing to do, for any one then could have entered and discovered him. But, no, after all, it was the sensible thing to do from his point of view, since otherwise the prospective suspect would have been unable to enter the room. Then I looked at McKelvie with dawning horror in my eyes. The unlocking of that door could have meant only one thing, that the criminal knew Ruth was across the hall, and deliberately, cold-bloodedly, planned to saddle her with the murder of her husband!
"Why, McKelvie," I began, horrified, but he tread on my toe as if by accident, and I recalled hastily that we were not alone.
"Even if I had not heard Mr. Darwin unlock the door," continued Orton ingratiatingly, "he must have unlocked it at some time, for I heard him turn the key in the lock when I left him at eleven-thirty and the door was open when Mrs. Darwin entered the room. But, I know I'm not mistaken in saying that I heard it unlocked."
"How do you know that it was Mr. Darwin who unlocked it?" I asked injudiciously.