"The door… why, always locked, sir. Invariably. It was never used."
Dr. Fell nodded. "And the lock," he said musingly, "isn't a spring-lock. It's the old-fashioned kind, d'ye see. Where's the key for it?"
The other reflected for some time. "I believe, sir, that it's hanging up on a hook in the pantry, along with some other keys for rooms that aren't used."
"Cut along then, and see if you can find it. Ill give you odds it isn't there, but have a look anyway."
He watched owlishly until the valet had left the room.
"Let's pass over for the moment," he went on, "the identity of the man who came to see Depping last night. Let's only assume that somebody came here for the purpose of killing Depping, not blackmailing him, and go on from there. Come here a moment, will you?"
They followed him uncertainly as he went over to the bridge lamp near the front windows.
The electric fittings in this place" he continued, "are of a rather old-fashioned variety. You see that socket along the baseboard of the wall? This plug," — he picked up a length of wire from the lamp—"this plug, which is loose now, is screwed into that socket. In the modern ones the plug has only two prongs, which fit into the socket, and the live part isn't exposed for somebody to touch accidentally and get the devil of a shock. But the live part is exposed there; you see?"
"Certainly," said the bishop. "What about it?"
"Well, I've found the buttonhook."