Together they hurried down the stairs to the little room where the wedding gifts were on display. Mark started across toward the mirror. The professor's hand shot out. Caught the younger man's arm. "Stand back!" he cried in a terrible voice. "Do not go near that mirror. Above all, do not pass in front of it!" Mark stared at the savant open-mouthed. His earlier black despair was gone, now, replaced by sudden, inexplicable hope. "Why not? What's wrong?" The other licked dry lips. "Nothing, I hope. The chances are a thousand to one that I am wrong. Yet an idea came to me, my boy. An incredible idea, and a horrible one. And if it is right"--he shook his head slowly--"may God have mercy on Elaine!" Carefully, then, they approached the mirror. The professor studied it through narrowed eyes from a vantage-point far to one side. At last he turned to Mark. "Do you notice any defects or flaws in the surface of that glass?" he demanded. His daughter's fiance nodded. "The whole thing's out of kilter, professor." "How would you describe it? What do you mean by 'out of kilter'?" * * * * * Mark considered for a moment. Then: "The impression I get is that this mirror was _poured_ into a circular form, instead of being cut to shape. And that while it was still molten, something struck it in the center, so that little ripples formed in the glass, all the way from the center to the outer edge." It was the scientist's turn to nod. "Precisely my own view." Moving away, he selected a candlestick and candle from among the gifts on display. He handed it to Mark. "I want you to move this stick in front of that glass," he instructed. "However, you must be careful to stand well to one side, so that you, yourself, will not be reflected." "What's the angle, professor? What do you expect to find? What's wrong with this mirror?" The elder man shook his head, moved to a point where he could watch the surface of the glass. "I do not know what to expect," he said. "I may be completely on the wrong track." But his flashing eyes denied the words. Seething with curiosity and excitement though he was, Mark carefully carried out his instructions. He moved the candlestick back and forth and up and down until it had been reflected from every inch of the mirror. And the farther he progressed, the more excited Elaine's father became. "The reflection is perfect!" the old man cried. "It is true! Nowhere is there a single sign of distortion!" "Yes. Of course it's true." Mark was a little bewildered. "Why shouldn't it be? Isn't every looking-glass supposed to throw back a reasonably exact image?" "Of course, of course!" The scientist was impatient. "But can you not see the difference?" "The difference? What difference?"