“That is the lesson of a finger-print. Tap A was stiff, and Mottram left a mark when he turned it on; he would have left another if he had turned it off. He did not; he turned off tap B, which works at a mere touch, and of course he left no mark in doing so. There, then, lies Mottram; the sleeping draught has already taken effect; the wind gets up, and blows the window to; tap A is still open, and tap C is still open; and through the burner of the standard lamp the acetylene is pouring into the room.
“Brinkman is not a late sleeper. The Boots, who is the earliest riser in this establishment, tells me that Brinkman was always awake when he went round for the shoes. On Tuesday morning Brinkman must have woken early, to be greeted by a smell of gas. It may have crept in through his window, or even come up through the floor, for the floors here are full of cracks. Once he had satisfied himself that the escape was not in his own room, he must have thought of the room below. When he reached the lower passage, the increasing smell of gas left him in no doubt. He knocked at Mottram’s door, got no answer, and rushed in, going straight across and opening the window so as to get some air. Then he had time to turn round and see what was on the bed. There was no doubt that he was too late to help.”
“Did he know it was accident?” asked Eames. “Or did he think it was suicide?”
“I think he must have known it was accident. And now, consider his position. Here was Mottram, dead by accident. There up in London was Mottram’s codicil, willing half a million to the Diocese of Pullford. And that codicil had not been meant to become operative. It had been made only for the purposes of the test. And now, through this accident, the codicil, which did not represent Mottram’s real wishes, had suddenly become valid. It would certainly be judged valid, unless—unless the claim were dismissed owing to a verdict of suicide. Brinkman may or may not have been a good man; he was certainly a good secretary. Put yourself in his position, Mr. Eames. He could only give effect to his dead master’s real wishes by pretending that his dead master had committed suicide.
“You remember the remark in ‘The Importance of Being Earnest,’ that to lose one parent may be an accident, to lose both looks like carelessness? So it was with Mottram and the taps. Two taps turned on meant, and would be understood to mean, an accident. But, and this is worth remembering, if all three taps were found on, it would look like suicide. Brinkman acted on the spur of the moment; he was in a hurry, for the atmosphere of the room was still deadly. He wrapped his handkerchief round his fingers, so as to leave no mark, then, in his confusion, he turned the wrong tap! He meant to turn tap B on; instead, he turned tap A off. That sounds impossible, I know. But you will notice that whereas tap A and tap B are turned off when they are at the horizontal, tap C is turned off when it is at the vertical, When Brinkman, then, saw the three taps, B and C were both horizontal, and A was vertical, it was natural, in the flurry of the moment, for him to imagine that if all three taps were in the same position (that is, all horizontal) they would all be turned on. Instinctively, then, he turned tap A from the vertical to the horizontal. And in doing so he left the whole three in the same position in which they were before Mottram lit his match. No gas was escaping at all. The result of Brinkman’s action was not to corroborate the theory of suicide, but to introduce a quite new theory—that of murder. Half-stifled, he rushed from the room, locked the door on the outside, and took the key away with him up to his room.”
“Steady on,” put in Angela, “why did he lock the door?”
“It may have been only so as to keep the room private till he had thought the thing out, and the Boots may have come round too soon for him. Or, more probably, it was another deliberate effort to encourage the idea of suicide. Anyhow, his actions from that moment onward were perfectly clear-headed. He helped to break down the door, and, while Ferrers was examining the gas, while the Boots was lighting a match, he thrust the key in on the inner side of the door. It was only when he had done this, when he thought that he had made the suicide theory an absolute certainty, that he was suddenly confronted with the horrible mistake he had made in turning the wrong tap. It was a bad moment for him, but fortunately one which excused a certain display of emotion.”
“And he thought he would be run in for the murder?” asked Leyland.
“Not necessarily. But your arrival worried him badly; you got hold of the murder idea from the start.”
“Why didn’t he skip, then? There was the car, all ready provisioned.”