"Since yesterday half a dozen theories have suggested themselves to my mind as possible explanations of this very daring murder, for I am now fully convinced that it is nothing less; but I make it a rule never to accept, much less announce, a belief, until I have established at least a reasonable series of corroborative circumstances. This I have not done entirely to my satisfaction, and so we will not go into the theory of the case, but will see what facts we have established; and fact number one, to my mind, is this: Your brother, Mr. Brierly, was most certainly shot down with malice aforethought. He could not have shot himself, and no one, in that open place, could have killed him by accident. He may have been entirely unaware of it, but he had an enemy; and the deed of yesterday was planned, I believe, long ago, and studied carefully in every detail."
Robert Brierly flushed and paled. He opened his lips as if to speak, but the detective's eyes were steadfastly turned away, and he resumed almost at once.
"I blame myself that I did not establish myself here last night, as I at first thought of doing. But it is too late for useless regret. And now, about this boy. Have you, either of you, a thought, a suspicion, as to his identity?"
The doctor shook his head.
"You can't suspect one of the pupils, surely?" hazarded Brierly.
"Be sure that Mrs. Fry knows every pupil in Glenville, by sight, at least; and this lad was a stranger, remember. It was a clever lad who first secured the key to these rooms and then decoyed Mrs. Fry half way across the town perhaps. How long must it have taken her, Doc, to go and come, in haste?"
"Quite half an hour, I should think."
"Well, we will assure ourselves of that later. Now we will suppose that this strange boy was acquainted with these rooms to some extent, and that he was, I fully believe. When Mrs. Fry is out of sight—and we know, from her story, that he was careful that she should be before he left his station upon the front porch—he slips indoors and evidently knows where to look for a lamp, which he does not light until he is inside this room." And Ferrars put a finger upon the match remarked upon by Mrs. Fry. "Now, as Mrs. Fry observed, there has been quite a film of dust in the air for the past twenty-four hours, so that, in spite of the good woman's tidy ways, it has accumulated upon this dark and shining wood." And he put down his finger and called their attention to its prints upon the table at his side.
"When we entered this room," he went on, "and I took it upon myself to look at that window with the swinging blind, under pretence of opening the shutters, I first noted that the visitor had left us a clue to his identity—several clues, indeed. Before seeing these I had thought that the boy was only an advance guard for some one else, but I see I was wrong. It was the boy, and a very keen and clever boy, who entered here alone. See upon this table, upon the window sills, and upon the desk, the prints of one, two, and sometimes all four, small slender fingers."
Ferrars paused a moment, while they examined the dust prints, faint but yet clear, upon the dark wood, and making lines of clearer colour upon the painted brown of the window sills.