"How do you plan to find your aliens--if there are any?" "Search pattern." Lanko shrugged. "We'll cruise around in a grid pattern until we pick up some sort of reading, or until we spot something abnormal." He pointed at a series of instruments. "They're bound to have a ship somewhere, and we'll pick up a small amount of power radiation from their screens. If their ship were orbiting in space, we'd have picked it up long ago, so we must assume it's grounded. I think we'd better go right into a pattern. We can use Kneuros as origin." He stared at the plotting instruments. "Let's see. If I wanted to hide a ship, I'd use the most inaccessible location I could find. We do that ourselves, in fact. And there are some mountainous regions inland." He set up course and speed. "Yeah," Banasel added, "and I'd worry a lot more about ground approach than air accessibility, at least on this planet." The ship gained altitude, accelerated, and sped eastward. Day by day, the course trace built up, the cameras recorded the terrain under the ship, and the two guardsmen built up their mosaic. The ship crossed and re-crossed the continent, mapping as it went. From time to time, Lanko made careful comparison of the new mosaic with an earlier survey, noting differences. There were new settlements. Where members of a nomadic culture had roamed the prairie, an industrial civilization was rapidly growing. Lanko tapped on the map. "Two cultures," he observed. "Two cultures, separated by mountains and desert. Absolutely no evidence of contact, but considerable similarity between them. This pattern begins to look familiar." He picked a tape from the shelves, ran it through a viewer, then reversed it, and picked out various portions for recheck. Finally, he made a superposition of some of their observation tape, examined it, and turned. Banasel held up a hand. "Don't tell us," he growled. "I studied about drones, too." "Drones?" Musa looked at him, then glanced back at the viewer. "Yes. Characters from one of the advanced cultures, who feel frustrated, and fail to fit in. They often turn into pleasure seekers, and frequently end up by monkeying with primitive cultures, to prove their ability to themselves, at least." "Things like this happen often?" "Oh, not too often, I suppose, but often enough so that people like us are stationed on every known primitive planet, to prevent activity of the type. You see, the drones usually start out simply, by setting up minor interference in business or government on some primitive planet. Usually, they're caught pretty quickly. But sometimes they evade capture. And they can end up by exerting serious influence in cultural patterns. Some planets have been set back, and even destroyed as a result of drone activity. Although their motives are different, drones're just as bad and just as dangerous as any other criminal."