"I'll tell you briefly the points that have made the matter at last clear, in spite of yourself," I said, reassuringly. "Tell me this, first,--when you came into the house that evening, after you left the boys at the banquet, was the house lit up or dark?"
"Dark. I lit the gas in the library. I did not go into the rest of the house."
"Exactly. Well, I saw the gas lit in the library that evening, and it was just a few minutes before ten. I had supposed that your sister and at least one servant were in the house, but I have learned they were not. Therefore, when I saw the light flare up just before ten in the library, you were there."
"Yes," he said, trying to follow.
"You threw yourself down on the couch and read Cicero from a book which the next day was in the hands of Chapman. You don't know how long you were reading, but you were sound asleep on that couch at three o'clock the next morning, for your sister came in and saw you."
"Jean?" he murmured, perplexedly.
"Yes, Jean. Never mind the details. Now it is not humanly possible that after reading yourself quiet at ten you could have reached Barker's office by foot before I reached there in a taxicab so as to secrete yourself in the inner room before I came. Neither is it humanly possible that after shooting him at eleven, you could have fled for your life down the fire-escape, skulked through the streets, and then come home and gone composedly to sleep by three, only to wake at six and remember for the first time that a gentleman who has had the misfortune to shoot a man is in honor bound to give himself up to the law."
He drew his hand over his eyes in a dazed fashion.
I went on. "Minnie, the maid, and her escort, came home at three that night and saw a man leaving the house by the library door. She took for granted that it was you. But your sister came into the room a few minutes later and saw you asleep on the couch. The man who left the house was not you."
"Who was it?" he asked, very low.