"But they did," said Dr. Fell. "That's exactly what they wanted to do. Haven't you looked in the fireplace? Haven't you wondered about afire in the hottest part of August? Haven't you seen that heavy, clotted mass of ash? Haven't you wondered what must have been burned, so that all the windows had to be raised?"
"You mean-"
"Clothes," said Dr. Fell.
There was an eerie pause. "I mean," the doctor went on, his voice rumbling through the quiet room, "I mean that glaring check suit worn by the visitor. You can still see traces of it in the fireplace. Now, mark you, these two are acting in perfect accord and understanding. The more we examine the problems as it seems to be, the more we must realize that it's mad, and there must be something wrong with the facts as they have been presented to us. Here is Depping admitting a visitor as he does, when he could easily have let him in through the balcony door without fuss. Here are Depping and his visitor sitting down to burn the visitor's clothes: which, I can assure you, is a social pursuit somewhat rare in the British Isles. Finally, we have the visitor not only shooting Depping with Depping's own gun, but (a) taking the gun out of the drawer without any protest, (b) getting behind Depping with it, also without protest, (c) firing two bullets of which one has mysteriously vanished, (d) carefully replacing the gun in the drawer, and (e) leaving this room by means of a balcony door which is always kept locked, and whose key is downstairs in the pantry."
Wheezing, the doctor took out his pipe and tobacco pouch with an air of gentle protest. Morley Standish, who had been staring out of the window, turned suddenly.
"Hold on, sir! I don't follow that. Even if Depping didn't let the man in, he might have got the key out of the pantry and put it in the door so that he could let the visitor out afterwards."
"Quite so," agreed Dr. Fell. "Then why isn't the key
there now?" "Why isn't-?"
"H’mf, yes. It's not very complicated, is it?" the other asked anxiously. "If you're a murderer leaving a room in comparative haste, throwing the door open and ducking out, does it generally occur to you to pinch the key on your way out? Why should you? If you wanted to lock the door behind you, I could understand the position. Lock the door; chuck away the key. But why, if you intend leaving the door ajar, do you want a dangerous souvenir like that?"
He lit the dregs of his pipe.