Babs' room! It sent a pang through me. A few of her garments were lying around. A negligee was laid out on the large bed. A velvet boudoir doll--she had always loved them--stood on the dresser. Upon this Hotel room, in one day, she had impressed her personality. Her perfume was in the air. And now she was gone. "We won't be here," Alan was repeating. He gripped me at the window. "Look." In his hand was an ugly-looking, smokeless, soundless automatic of the Essen type. "And I've got another one for you. Brought them with me." His face was white and drawn, but his hands had steadied. The tremble was gone out of his voice. "I'm going after him, George! Now! Understand that? Now? His place is only thirty miles from here, out there in the mountains. You can see it in the daylight--a wall around his property and a stone castle which he built in the middle of it. A gold mine? Hell!" There was nothing to be seen now out of the window but the snow-filled darkness, the blurred lights of Lower Quebec and the line of dock lights five hundred feet below us. "Will you fly me, George?" "Of course." I was the one trembling now; the cool feel of the automatic which Alan thrust into my hand seemed suddenly to crystallize Babs' peril. I was here in her room, with the scent of her perfume around me, and this deadly weapon was needed! But the trembling was gone in a moment. "Yes, of course, Alan. No use talking to the police. I gave them all the information--a description of her, what you said she was wearing. No sense dragging Polter's name into it, with nothing tangible to go on. The police won't ransack the castle of a rich man just because you can't find your sister. Come on. You can tell me what this place is like as we go." * * * * * Bundled in our flying suits we hurried from the Hotel, climbed the Citadel slope and in ten minutes were in the air. The wind sucked at us. The snow now was falling with thick, huge flakes. Directed by Alan, I headed out over this ice-filled St. Lawrence, past the frozen Ile d'Orleans, toward Polter's mysterious mountain castle. Suddenly Alan burst out, "I know what father's secret was! I can piece it together now, from little things that were meaningless when I was a kid. He invented the electro-microscope. You know that. The infinitely small fascinated him. I remember he once said that if we could see far enough down into smallness, we would come upon human life!" Alan's low, tense voice was more vehement than I had ever heard it before. "It's clear to me now, George. That little fragment of golden quartz which he wanted me to be so careful of contained a world with human inhabitants! Father knew it, or suspected it. And I think the chemical problem on which he was working aimed for some drug. I know it was a drug they were compounding, Polter said so once, a radioactive drug; I remember listening at the door. A drug, George, capable of making a human being infinitely small!"