"How should I know?" I retorted glumly. "It's my opinion he was liable to do anything."
"He could hardly be cognizant of the fact that Orton was prowling around, and he could easily turn off the lights when he heard footsteps crossing the hall. That's doubtless just what he did, which would imply that he was somewhere near the door. What a pity Orton caught no glimpse of him! He would hardly leave Mrs. Darwin's entrance to chance. He'd want to know when she was coming, for he couldn't be certain of the time she would choose to enter, no, not if he were twice as clever." McKelvie was thinking aloud, his brows knit once more, but I did not hesitate to interrupt him. There was no Jenkins present to preserve the flow of his thoughts undisturbed.
"You seem to believe, or rather I should say, you seem absolutely convinced that the criminal knew that Ruth would come to the study. The same conviction, with all its attendant horror, flashed over me a while ago when you were questioning Orton. But, upon my honor, now I review the thing calmly, I can't figure on what you base your conclusion. Ruth had no more idea of going into that study than I had, until I suggested it to her on the spur of the moment. That's the truth. How are you going to get around it?" I said emphatically.
He pulled a briar pipe from his pocket and lighted it before he answered. "That's easy. The criminal was in the room when Orton came in at eleven-thirty. Probably he was hiding in the safe in the secret room——"
"I thought you deduced that the criminal knew nothing of the secret entrance until he forced the knowledge from Darwin just before he killed him," I pointed out.
"I said he did not enter that way, not that he had no knowledge of it. Orton said that Darwin and his visitor were quarreling. Darwin knew his secretary and divined that he'd be hanging around the door listening. So he called him in and got rid of him, in the meantime hiding his visitor in the safe, from which point of vantage he heard the conversation between Orton and Darwin. Am I correct so far?" he inquired.
"Sounds plausible enough," I replied.
"Knowing human nature (I make this deduction because throughout he has most certainly traded on his knowledge of human beings in general, and the police in particular), he put himself in your place. What would he do if he were in love with Mrs. Darwin and had learned of the existence of the letter. Why, naturally urge Mrs. Darwin to try to secure the incriminating evidence. So you see he was pretty sure she would come, but he did not know when. He couldn't possibly know when, could he?" he asked appealingly.
"No, I don't at this moment see how he could, unless he was a magician, which isn't likely. I think myself we are on the wrong tack altogether. We are trying to complicate a simple affair. The criminal, no doubt, came in at midnight and shot Darwin without knowing that Ruth was there. Then he went off again through the secret entrance, and Ruth was implicated by pure chance, for, after all, there is only one pistol, there was only one shot heard, and only one bullet found," was my contribution.
"All I can say to that, Mr. Davies, is that in that case the murderer must have been a magician after all, for surely you are not implying that Mrs. Darwin lied when she said the study was dark?" he remarked with a smile, blowing wreaths of smoke along Broadway, for we were driving slowly toward town.