"I want you to know," the professor had added in a sober tone, "that if you come with us you may be in some danger; in fact I'm quite certain that I can promise it, yet it will never be foolhardy nor reckless danger. You'll come to live with us. That is necessary." "That's O.K.," Johnny had agreed. And now Johnny found himself outside in the cool air of night, the lake breeze fanning his cheek, wondering if it all--the living skeletons, eyes blinking in the wall, the self-closing doors--all had been a dream. "No!" He crushed the roll of bills in his pocket. "No, it was real enough. I--" Suddenly two shadows materialized from a doorway, one tall, one short. "The--the two men of the living skeletons, the ones that girl and I saw in the mirror!" he whispered, catching his breath sharply. If there had been any question in his mind regarding this last conclusion it was dispelled instantly. An inch of white steel, a knife blade, protruded from the short person's sleeve as he muttered menacingly, "Stand where you are!" CHAPTER II SOMETHING RATHER TERRIBLE Johnny Thompson was no weakling. He was a lightweight boxer. He had made his way over the frozen wastes of Alaska and through the jungles of Central America and many other wild places as well. This city held little terror for him. As he faced the two strangers in the semi-darkness of the street, he considered tackling the little man. "If I tackle low I'll catch him off his guard, bowl him over like a tenpin. But the other, the tall one?" Ah, there was the rub! He carried a knife at his belt. The boy could run, but at thought of that he seemed to feel a twinge of pain from a knife in his back. As he stood there, nerves all aquiver, oddly enough he thought of the mysterious eye blinking out of the wall back there in the hall. He wondered vaguely what it all meant and how this affair was to end. And then quite suddenly the affair of the moment ended. The tall man uttered a low grumble which Johnny did not understand. Next instant the pair faded into the darkness, leaving him free to go his way in peace. "Strange business, all of this," he murmured to himself. He felt for the roll of bills that had been paid him for the professor's library. Yes, they were still there. "He said, 'Come back tomorrow.' The professor said that," he mumbled as he hurried away. "Said I would meet dangers. W-e-l-l--" He walked three blocks in deep thought. The whole business had thus far been very strange. What of the future? How little he knew! Tomorrow lay before him, and after that tomorrow and another tomorrow. The task he had agreed to undertake was strange beyond belief. Yet, for the most part ignorant of all this, he slept well that night and appeared next morning, suitcase in hand, ready for work at the door of that mystery house. In the broad light of day the place had lost much of its air of mystery.