Up the stairs by a milliner’s shop, past the third story, to the fourth, we climbed. A wing ran back, with a gallery that opened on one side. At the rear was a short flight of steps, with a scuttle at the top, which opened out on the roof. By good fortune, this was unlocked, and we climbed through, out on the flat roof, into the maze of chimneys. Tom was a little ahead and reached the parapet on the side of Number 9, while we were still at the scuttle. As he turned to the edge, he wheeled and beckoned to us expressively. We hurried forward. Below, on the fourth story, three shuttered windows faced us. In the centre one, the wind had blown half the blind open. Behind it, we gazed on a solid wooden panel, which filled the window from top to bottom, from side to side, behind the glass. “An exact duplicate of the window panels of Heidenmuller’s wooden room,” I whispered. Tom and Dorothy nodded silently. CHAPTER XVI Quietly we drew back from the parapet and, closing the scuttle behind us, started down the narrow stairs. At their base, Dorothy stopped suddenly. As Tom came up, he noticed her delay and paused with his hand on the latch. “What is it, girl?” he asked, almost tenderly. “You think we ought to go on, do you?” asked Dorothy hesitatingly. “Of course we’re going on,” said Tom. “There’s no question about it. That’s what we’re here for. What’s the matter, anyway?” “Frankly, I don’t know,” said Dorothy slowly. “If we come through this all right, I’ll try never to say a word again, but somehow,--somehow--” She broke off without finishing. “Cheer up, old girl,” comforted Tom, putting his arm about her waist. “What should we do without your valiant spirit?” I stood there mute. This was a new Dorothy, a silent, questioning woman different from the one I knew, and yet like her. I could not seem to collect my scattered wits enough to be of any service. With an effort, Dorothy squared her shoulders. “Come on,” she said firmly, and we started out for the door, Tom and I a couple of steps behind. “Good for you,” I whispered, as we turned in beside the haberdasher’s shop and started up the stairs, at whose top we were forced to believe stood the laboratory of the man we sought, the workshop of the man who was trying to stop all war. As we reached the second landing, Tom turned to me. “This is the queerest mixture of fireproof and firetrap I ever heard of,” he ejaculated. “Iron stairs and wooden landings, with two doors on each side. Wonder if it keeps on like this all the way up?” It did; iron stairs and wooden landings succeeded each other, till the fourth story showed two doors, one on either side of a landing dimly illuminated by a skylight. “It’s one of the two,” whispered Tom.