He paused a moment and there was a tense silence. A great light was coming to Hatch, slowly but surely. The brain that had followed all this was unlimited in possibilities.
"Even before we traced the origin of the crime to this room," went on the scientist, quietly now, "attention had been attracted here, particularly to you, Mr. Cabell. It was through the love affair, of which Miss Lipscomb was the center. Mr. Hatch learned that you and Henley had been rivals for her hand. It was that, even before this scarlet thread was found, which indicated that you might have some knowledge of the affair, directly or indirectly.
"You are not a malicious or revengeful man, Mr. Cabell. But you are hot-tempered--extremely so. You demonstrated that just now, when, angry and not understanding, but feeling that your honor was at stake, you shot a hole in the floor."
"What?" asked Detective Mallory.
"A little accident," explained The Thinking Machine quickly. "Not being a malicious or revengeful man, you are not the man to deliberately go ahead, and make elaborate plans for the murder of Henley. In a moment of passion you might have killed him--but never deliberately as the result of premeditation. Besides you were out of town. Who was then in these apartments? Who had access to these apartments? Who might have used your bath robe? Your valet, possibly Miss Austin. Which? Now, let's see how we reached this conclusion which led to the valet.
"Miss Regnier was found dead. It was not suicide. How did I know? Because she had been reading with the gas light at its full. If she had been reading by the gas light, how was it then that it went out and suffocated her before she could arise and shut it off? Obviously she must have fallen asleep over her book and left the light burning.
"If she was in this plot to kill Henley, why did she light the jet in her room? There might have been some slight defect in the electric bulb in her room which she had just discovered. Therefore she lighted the gas, intending to extinguish it--turn it off entirely--later. But she fell asleep. Therefore when the valet here blew into the pipe, intending to kill Mr. Henley, he unwittingly killed the woman he loved--Miss Regnier. It was perfectly possible, meanwhile, that she did not know of the attempt to be made that particular night, although she had participated in the others, knowing that Henley had night after night sat up to watch the light in his rooms.
"The facts, as I knew them, showed no connection between Miss Regnier and this man at that time--nor any connection between Miss Regnier and Henley. It might have been that the person who blew the gas out of the pipe from these rooms knew nothing whatever of Miss Regnier, just as he didn't know who else he might have killed in the building.
"But I had her death and the manner of it. I had eliminated you, Mr. Cabell. Therefore there remained Miss Austin and the valet. Miss Austin was eccentric--insane, if you will. Would she have any motive for killing Henley? I could imagine none. Love? Probably not. Money? They had nothing in common on that ground. What? Nothing that I could see. Therefore, for the moment, I passed Miss Austin by, after asking you, Mr. Cabell, if you were Miss Austin.
"What remained? The valet. Motive? Several possible ones, one or two probable. He is French, or says he is. Miss Regnier is French. Therefore I had arrived at the conclusion that they knew each other as people of the same nationality will in a house of this sort. And remember, I had passed by Mr. Cabell and Miss Austin, so the valet was the only one left; he could use the bath robe.