Garth moved quietly to the door. Through the grill he saw the cave, empty of life. There were no guards. He was glad he had slept past dawn, so that the Zarno were able to believe him entranced like the others. But what now? Escape? To where? There was still power in the lost city; perhaps the weapons of the Ancients still existed. Weapons stronger than guns to conquer the Zarno! But, regardless of that, it was necessary to find a hiding-place. This was the day of sacrifice. Ironic thought--a hiding-place in an underground city teeming with the Zarno! Garth shrugged. The door was locked, he discovered, and it took time to find the twisted wire Sampson had used. Even then, Garth was unable to manipulate the intricate tumblers. He scowled, chewing his lip, and eying the wire. Sampson's skilled fingers were necessary. He roused the red-haired giant and led him to the door. Sampson looked straight ahead, his eyes dull. He obeyed when Garth spoke--but that was all. Was his skill sufficiently instinctive to be used now? There was only one way to find out. Garth put the wire in Sampson's hand. "Unlock the door." He had to repeat the command twice before Sampson understood. Then the big man bent, fumbling with the lock, working with agonizing slowness. Hours seemed to drag past before Sampson straightened. * * * * * Garth tried the door. It opened. The first step was accomplished, anyhow. The others would be more difficult. He was unfamiliar with the underground city. How the devil could he evade the Zarno and find a hiding-place? Alone, he would have a better chance. But he had twelve companions to take with him. He spoke to each of them. "Follow me. You understand? Follow me till I tell you to stop. Move as quietly as you can." Then he led them out of the cell. The city, as he speedily learned, was a labyrinth. Luckily there were innumerable cross-passages. And all the cities of the Ancients had been built along a similar plan. Garth knew the layout of Chahnn, and that helped him now. But there were times when he had to move fast, and the others walked as though striding through water. "Quick! In here! _Fast!_" And they would follow him, into a side tunnel, while the heavy, metallic foosteps of the Zarno approached like the drums of doom. But there was no place to hide permanently. Worst of all, a distant clanging sounded presently, and Garth guessed what that meant. The escape of the captives had been discovered. Gingerly he skirted the huge cave where the dais was, glimpsing the giant robot in the distance, and shepherding his charges along a twisting corridor that led down. But the footsteps were growing louder. Garth was almost certain that they were following. He increased his pace, with wary glances behind him. Unless he found a side passage soon, the swift Zarno would speedily overtake them. "Faster! Move faster!"