Starting from the first square, the path went left, straight, right, right, right. And after zero, the numbers went 1, 2, 3, 3, 3. Apparently he had found the key. One meant a square to the southeast; two meant south; and three southwest. Shivering, he moved up to the fifth square upon which the monster growled his first warning. He looked back at the door, then at Big Joe. The taloned hands could grab him before he could dive back into the corridor. He hesitated. He could either turn back now, or gamble his life on the accuracy of the tentative belief. The girl was calling to him again. "Come to the end of the corridor!" he replied. She came hurriedly, to his surprise. "_No!_" he bellowed. "Stay back of the entrance! Not on the tile! _No!_" Slowly she withdrew the foot that hung poised over a trigger-tile. "You can't come in unless you know how," he gasped. She blinked at him and glanced nervously back over her shoulder. "But I hear them. They're coming down the stairs." Asir cursed softly. Now he _had_ to go ahead. "Wait just a minute," he said. "Then I'll show you how to come through." He advanced to the last tile that he had tested and stopped. The next two numbers were two--for straight ahead. And they would take him within easy reach of the long taloned arms of the murderous sentinel. He glanced around in fright at the crushed bones scattered across the floor. Some were human. Others were animal-sacrifices tossed in by the priests. He had tested only one two--back near the door. If he made a mistake, he would never escape; no need bothering with the pike. He stepped to the next tile and closed his eyes. "_If the intruder makes an error, Big Joe will kill._" He opened his eyes again and heaved a breath of relief. "Asir! They're getting closer! I can hear them!" He listened for a moment. A faint murmur of angry voices in the distance. "All right," he said calmly. "Step only on the tiles I tell you. See the gray one at the left of the door?" She pointed. "This one?" "Yes, step on it." The girl moved up and stared fearfully at the monstrous sentinel. He guided her up toward him. "Diagonally left--one ahead--diagonally right. Now don't be frightened when he speaks--" The girl came on until she stood one square behind him. Her quick frightened breathing blended with the growing sounds of shouting from the stairway. He glanced up at Big Joe, noticing for the first time that the steel jaws were stained with a red-brown crust. He shuddered. The grim chess-game continued a cautious step at a time, with the girl following one square behind him. What if she fainted again? And fell across a triggered tile? They passed within a foot of Big Joe's arm. Looking up, he saw the monster's eyes move--following them, scrutinizing them as they passed. He froze. "We want no plunder," he said to the machine. The gaze was steady and unwinking. "The air is leaking away from the world." The monster remained silent.