Jan's eyes pulled away from this fascinating thing and turned to survey what had first caused him to break his pace in surprise. A short distance away a skeleton of twisted and sheered off steel girders hinted at what had once been a bridge across a deep gash in the rolling terrain. On the other side was what had once been a huge city of sky-scrapers, though Jan had never heard of such a thing and did not know that that was what it had been. [Illustration: Nothing was visible in the mysterious plate, yet a man had gone into it!] With a frown of uneasiness he dismissed the ruins of the city and the bridge and turned to the mysteriously glowing square once more. The deer had vanished over it. Therefore it must have something to do with the vanishing of the deer. Since he had chased the deer so far, it would be foolish to turn away without investigating. The deer might still be there somewhere. Jan's face lit up with an idea. He looked around until he spied a rock about as big as a fist. He came back with it and stood thoughtfully near the edge of the mysterious square. Then he tossed it with just enough force to carry it across. When it reached a point above the edge of the square it vanished. Jan waited, but it didn't land on the other side. It had simply ceased to exist! Jan looked thoughtful for a moment. He turned and went back to the patch of blackberry bushes. Taking his long slim blade from its deerskin scabbard he cut a long, tough stick, trimming the younger shoots away. With this he returned to the calmly glistening, mysterious slab. Ready to drop his hold on the stick at the first sign of the unusual, he thrust it part way into the area where things vanished. The end of the stick disappeared. There was no sign of any force creeping along the stick to his hand. He waited, reassuring himself. Then he stuck the stick in a little farther and it vanished a little farther along toward his hand. He held it that way, his nostrils flaring with tenseness. Then slowly he drew the stick back. The vanished part of it returned to sight. It came out and was not changed in the least. He sniffed at it. It smelled no different than it should. He felt of it carefully. It felt normal. Reassured, he thrust it into the area of vanishment again. He pulled it out again. It delighted him to watch it vanish and reappear. He laughed gleefully. The deer was forgotten in the excitement of this strange game in the shadow of the crumbling bridge. Suddenly the vanished end of the stick jerked in his hand. In spontaneous alarm he pulled toward him. The stick came unwillingly. Something held it. * * * * * Terrified, Jan dug his heels in the turf and pulled. Slowly inch by inch, the stick reappeared. But with it appeared a fat, pale hand, followed by a sleeved arm.