"H’mf. I'm only theorizing now, of course," the doctor rumbled, "yet, when you ally it with a few other points I shall indicate in a moment, it is an alluring theory. That's the only way the trick could have been worked. Yet again the total adds up to foolishness if we conceive that — as a part of this intricate design— Depping provided himself with a pair of rubber gloves to put out his own lights, when (as I have insisted) other and simpler methods were at hand… Nevertheless, there is another connotation of rubber gloves. If a man desires to leave no fingerprints, and yet have a free and delicate use of his hands, rubber gloves are the best sort of protection."
The bishop made a massive gesture. "My dear Dr. Fell," he intoned, almost sepulchrally, "you are getting into the realm of fantastic nonsense. Why should the late Mr. Depping have cared whether or not he left fingerprints in his own study?"
Letting out a gust of smoke, Dr. Fell leaned forward with a sort of fierce intensity and pointed his pipestem. His wheezing breath grew louder. He said:
"Exactly! Why should he? There's another, Why should he for this incredible collection. Why should he at least not make a pretense of wondering why the lights went out? Why didn't he play his part like an artist, and come out of his room to ask Storer what was wrong? Why didn't he show himself? Why did he help the visitor burn his clothes? — And last of all," said the doctor, lifting his stick and jabbing it towards the dinner tray, "why did he sample everything on that tray except his favorite soup?"
"I say, this bears a curious resemblance to the classic history of the three bears. 'Who's been sitting in my chair? Who's been drinking my porridge? Who—' Gentlemen, I think you are beginning to perceive by this time that the man in this room was not Depping at all."
The bishop muttered something to himself. A sudden dazzling suspicion seemed to make him wheel round and look at the smirking face of the dead man…
"Then Depping—" he said. "Where was Depping all this time?"
"Why, I’ll tell you " responded the doctor, and made a hideous pantomime face by way of emphasis. "He was decked out in an eye-splitting check suit, bogus jewellery, a wig, a false moustache, and actor's cement behind his ears to make them protrude. He was ringing his own doorbell and paying a call in his own house… There it is, you see. In this masquerade the roles were simply reversed, and that's what I meant by saying we should have to tear apart the facts as they seemed, or we should never understand the truth. It was X, the mysterious stranger, who posed as Depping in this room. And it was Depping — eh?"
"Can you—" said Morley Standish, "can you prove this?" He was breathing hard, and his heavy dark face, with its absurd-looking moustache, had a sudden look of relief.
"I rather think I can," said Dr. Fell modestly.