He paused to gaze from one to the other. Hunt and Gray returned the look without speaking. Caldwell continued: "A team from one of the survey units was engaged in mapping out possible sites for clearance radars. They were operating in a remote sector, well away from the main area being leveled . . ."

As he spoke, Caldwell began operating the keyboard recessed into one side of his desk. With a nod of his head he indicated the far wall, which was made up of a battery of display screens. One of the screens came to life to show the title sheet of a file, marked obliquely with the word RESTRICTED in red. This disappeared to be replaced by a contour map of what looked like a rugged and broken stretch of terrain. A slowly pulsing point of light appeared in the center of the picture and began moving across the map as Caldwell rotated a tracker ball set into the panel that held the keyboard. The light halted at a point where the contours indicated the junction of a steep-sided cleft valley with a wider gorge. The cleft valley was narrow and seemed to branch off from the gorge in a rising curve.

"This map shows the area in question," the director resumed. "The cursor shows where a minor cleft joins the main fault running down toward the left. The survey boys left their vehicle at this point and proceeded on up to the cleft on foot, looking for a way to the top of that large rock mass—the one tagged 'five sixty.'" As Caldwell spoke, the pulsing light moved slowly along between the minor sets of contours, tracing out the path taken by the UN team. They watched it negotiate the bend above the mouth of the cleft and proceed some distance farther. The light approached the side of the cleft and touched it at a place where the contours merged into a single heavy line. There it stopped.

"Here the side was a sheer cliff about sixty feet high. That was where they came across the first thing that was unusual—a hole in the base of the rock wall. The sergeant leading the group described it as being like a cave. That strike you as odd?"

Hunt raised his eyebrows and shrugged. "Caves don't grow on moons," he said simply.

"Exactly."