"Mrs. Darwin, naturally."
"How on earth did he know she would come into the room? How could he possibly divine that I would urge her to get me that letter when I only spoke on impulse myself?"
McKelvie sighed. "I'm not omniscient. If I could tell you how he knew it, or why, I could tell you who committed the crime. I am only reconstructing what actually happened, for he was in the room at midnight, wasn't he, since he fired that second shot and lighted the lamp? And is it reasonable to suppose that it took him twenty minutes to shoot his victim and place him in that chair?"
I acquiesced, but not because I could see through the affair. It was growing more intricate with every step we took. "But why, man, why?" I persisted.
"Because he needed a scapegoat. It may be, of course, and probably is, the fact that he was about to leave when he heard Mrs. Darwin try the door, and that the idea then came to him to incriminate her."
"Why—that's monstrous!" I cried.
McKelvie shrugged. "When you are dealing with a murderer, his little ideas are apt to be rather outside the pale of civilized folk," he returned ironically. "By providing the police with a suspect he escaped their vigilance. Mrs. Darwin had the most motive for killing her husband; therefore, she made the best possible victim. But he figured without me. It's like a game of chess. He makes a move. I block him. At present it's 'check,' with all the advantage on his side and every prospect of the jury finding Mrs. Darwin guilty of the murder."
He had forgotten my presence and was talking to himself, his eyes grown dreamy as he gazed into the distance. At my exclamation, he passed a hand across his eyes, saying in a different tone, "I beg your pardon. I forgot in my interest in matching my wits against his, that to you Mrs. Darwin is more than a pawn in the game."
"McKelvie, surely you can't be serious," I implored him.
"I'm sorry to say that I am," he returned. "The prosecution has a very strong case, and we have nothing we can offer that refutes a single point that they can make." He moved away from the window, where he had been sitting for some little time, and began to pace the room in long, even strides.