"Thought-waves, that's it! Sure!" He leaned forward excitedly, and Jen told him frantically to lower his voice. "I'll be damned. They've been experimenting with sun-stones for years on Earth--ever since they were discovered, but the scientists never thought of...." "Do they have the stones on Earth, too?" asked Jen, with loathing. "No, no, only the ones that are brought from Mercury. Something about Mercury being so close to the Sun, overdose of solar radiation and the extremes of heat, cold, and pressure while the planet was being made, that formed that particular kind of crystal here. I guess that's why they're called sun-stones." He shook his head. "So that's how they work it--direct mental communication between the Korins and the hawks, by means of the stones. Simple, too. Set them right in the skull, almost in contact with the brain, and you don't need all the complicated machines and senders and receivers they've been monkeying with in the labs for so long." He shivered. "I'll admit I don't like the idea, though. There's something repulsive about it." Hugh said bitterly, "When they were only men, and convicts, we might have beaten them some day, even though they had all the weapons. But when they became the Korins--" He indicated the darkling alcoves of the cave. "This is the only freedom we can ever have now." Looking at Hugh and Jen, Trevor felt a great welling-up of pity, for them, and for all these far-removed children of Earth who were now only hunted slaves to whom this burrow in the rock meant freedom. He thought with pure hatred of the Korins who hunted them, with the uncanny hawks that were their far-ranging eyes and ears and weapons. He wished he could hit them with.... He caught himself up sharply. Letting his sympathies run away with him wasn't going to do anybody any good. The only thing that concerned him was to get hold of that sun-stone again and get out of this devil's pocket. He'd spent half a life hunting for a stone, and he wasn't going to let concern over perfect strangers sidetrack him now. The first step would be getting away from the cave. It would have to be at night. No watch was kept then on the ledges, for the hawks did not fly in darkness, and the Korins never moved without the hawks. Most of the people were busy in those brief hours of safety. The women searched for edible moss and lichens. Some of the men brought water from the stream at the canyon fork, and others, with stone clubs and crude spears, hunted the great rock-lizards that slept in the crevices, made sluggish by the cold. Trevor waited until the fourth night, and then when Saul's water party left, he started casually out of the cave after them. "I think I'll go down with them," he told Jen and Hugh. "I haven't been down that far since I got here." There seemed to be no suspicion in them of his purpose. Jen said, "Stay close to the others. It's easy to get lost in the rocks."