greenish in color as it swirled toward him in the damp vaulted passageway. His eyes began watering a little and the lining of his nose started to burn. He stopped short, newly alarmed, and stared at the walls, rubbing the tears away to clear his vision. The greenish-yellow haze grew thicker, catching his eyes and burning like a thousand furies, ripping into his throat until he was choking and coughing, as though great knives sliced through his lungs. He tried to scream, and started running, blindly. Each gasping breath was an agony as the blistering gas dug deeper and deeper into his lungs. Reason departed from him; he was screaming incoherently as he stumbled up a stony ramp, crashed into a wall, spun around and smashed blindly into another. Then something caught at his shirt. He felt the heavy planks and pounded iron scrollwork of a huge door, and threw himself upon it, wrenching at the old latch until the door swung open with a screech of rusty hinges. He fell forward on his face, and the door swung shut behind him. He lay face down, panting and sobbing in the stillness. Coarse hands grasped his collar, jerking him rudely to his feet, and he opened his eyes. Across the dim, vaulted room he could see the shadowy form of a man, a big man, with a broad chest and powerful shoulders, a man whose rich voice Harry almost recognized, but whose face was deep in shadow. As Harry wiped the tears from his tortured eyes, he heard the man's voice rumble out at him: "Perhaps you've had enough now to change your mind about telling us the truth." Harry stared, not quite comprehending. "The—the truth?" The man's voice was harsh, cutting across the room impatiently. "The truth, I said. The problem, you fool, what you saw, what you learned; you know perfectly well what I'm referring to. But we'll swallow no more of this silly four-dimensional superman tale, so don't bother to start it." "I—I don't understand you. It's—it's true—" Again he tried to peer across the room. "Why are you hunting me like this? What are you trying to do to me?" "We want the truth. We want to know what you saw." "But—but you're what I saw. You know what I found out. I mean—" He stopped, his face going white. His hand went to his mouth, and he stared still harder. "Who are you?" he whispered.