I was out of my seat with excitement. “I believe he is. Would you know him if you saw his photograph?” “Surely,” said Hamerly. I rose to go. “Hold on,” exclaimed Hamerly, “I haven’t told you half yet.” “Go on,” I said eagerly, seating myself once more. “That first day, after I had made a rough examination, I started to go over the inner room inch by inch. At first I thought it was perfectly insulated by wood. There wasn’t a piece of metal nor even a piece of glass in it. Where the incandescent light came down, hung a bit of twisted cord, without a scrap of metal remaining. There was a length of insulating cloth, minus the wire it covered, lying on the floor. I went round and round, hunting for metal, but I could find none. There was a wooden shutter over the window, and no glass. I closed the door and walked over every inch of the room, trying to find any break whatsoever in the insulation. The only thing I could find was a faint glimmer, where the wooden window shutter did not quite join. I went outside and studied the place from the street. There was no appearance of anything unusual on the wall of the laboratory, excepting that the boarded window of the wooden room looked out like a rectangular unseeing eye. I crossed to the sidewalk just before the laboratory, and looked up and down the opposite wall. There was nothing unusual on that side, save two square places, side by side on the painted wall, which looked fresher than the wall around. I examined them more carefully, crossed and recrossed. The two spots were almost exactly opposite the lower end of the shuttered window where I had seen a slight chink of light, the only place where the insulation of wood was broken. I went up the stairs of the house opposite. It was a little tea shop. A wooden sign leaned against the wall beside the door. I picked it up. The screw holes and the whiter paint where the hinges had lain showed clear, but there was no metal about it. The proprietress bustled up to take my order and, as she saw me looking at the sign, broke into voluble explanation. ‘I should have put the sign back in its place, sir, but fairly didn’t dare to. It was a week come Tuesday when it fell. It’s God’s own mercy there wasn’t somebody killed, sir. And the strangest thing, too. I couldn’t find sight nor smell of the hinges and the rod where it hung. It must have pulled out of the wall, and somebody have picked up the iron, before I could get down, sir. Now isn’t that strange, sir?’ “It had fallen the day that Heidenmuller died.