When the siren blew Hanlon smiled happily at his crew as he herded them together, and made applauding motions with his hands, wondering if they understood what he meant. When he had locked the natives in their stockade, he hunted up the checkers. "How'd I do?" he asked. "Come anywhere near what I was supposed to get out?" One of the checkers totalled up his figures, then looked up in surprise. "Hey, kid, you did all right. Nearly a hundred pounds over the usual output, and clean, too. That's really okay for a new guard, and then some. Didn't have any trouble, eh?" "Trouble?" Hanlon asked naively. "Was I supposed to have some?" Then he couldn't help grinning. "Thanks for the info," and went to his room, took a shower to cool off after that muggy heat in the mine, then tumbled onto his bunk for a nap until dinner-time. Those first days so thoroughly disgusted George Hanlon as he saw the continued and senseless brutality the guards used toward their native "slaves," that he had trouble concealing his feelings. He continued to treat his Greenies with the respect he felt was due them, and he could not help but notice they seemed to look on him more and more as their friend. They always smiled when he looked at them, and before many days he discovered that his crew was doing more work than any of the others. His mind-probing had convinced him they were high enough in the scale of evolution to know the meaning of gratitude, and he could tell they were repaying his kindness with co-operation. He had begun to make much more sense out of the pictures he saw in their minds, and to get some glimmerings of understanding about their alien concepts. Also, it was increasingly borne in upon him that they did "talk" to each other, and he guessed shrewdly that the reason no one could hear them was because their voices were above ... or below? ... the range of human hearing. "Above," he finally deduced. That gave him the idea for an experiment, and he started whistling as loud as he could, gradually raising his tones until he was at the top of his range. He saw with interest and excitement that the last one or two shrillest notes seemed to attract their attention. Their silly-looking little triangular ears perked up and began twitching. They turned about, as though seeking the source of that sound, while every mouth began working with signs of utmost excitement, and his mind caught concepts of surprise and wonder. That convinced him and so, in his next several off-hours, he surreptitiously collected various articles and pieces of material, and in his room started the construction of a little machine. His course in the Corps school had included considerable mechanics and electronics, and the tearing down and rebuilding of many of the machines and instruments the Corps used.