There it was, with two windows to the street and both closed; it was winter, you see, and Sencort wasn't the only near octogenarian to rally round that walnut. It had electric lights and nothing else but a steam radiator, carpet and chairs and five old etchings on the walls. Everything was clear; nothing was wrong in the drawers or under the tables or chairs or even under the carpet. Reed had carefully tested the radiators and steam pipes. They were absolutely in order.
But I kept poking about the room and, behind an etching, I found the capped head of an old gas pipe which evidently brought illuminating gas to the room in the days before electric lighting.
It was capped, I say, and looked quite all right, but I happened to put my fingers behind the cap. Then I called Teverson; and he felt, and called Reed.
"What do you think of that?" he asked.
That was a slot—rather a series of slots—cut through the pipe behind the cap on the right wall. You couldn't see them from the front; you hardly could see them when you pressed cheek to the wall but you could feel them top, bottom and sides of the pipe cut through, leav-
