His father squinted. "There's a powerful vibrational effect. It may be a very dangerous concentration of the invisible rays of the Sun as well as of light."
Once Burl had gotten used to the odd visual effect, which was like gazing into the twisting heat rays rising from an overheated oven, he saw that there was a small flat region between the mountains. And in the center of this valley was a large black structure of some sort. The twisting effect of the light around it made it impossible to tell more.
"That's it," said Burl. His father nodded, shifted the pack to ease his shoulders, unstrapped the hunting rifle slung over his back, and carefully checked its loads.
Burl saw what his father was doing and suddenly understood the danger. What could be doing a thing like this? What but something not of this Earth? Something of distant space, of a science beyond that of man—and unfriendly besides. Now, for the first time, Burl realized what he had not had time to before—this was an enemy he and his father were facing—an enemy of all mankind—and utterly unknown.
He gulped, gripped his rifle, and followed his father down the sliding rocky trail.
As they drew nearer the base of the mountain, the effects of the strange vibrations grew more pronounced. Burl avoided looking directly ahead, keeping his eyes on the ground before his feet, yet even so, he could not help noticing how the stones around them seemed to shimmer in the invisible waves. From the base of the valley the sky now seemed streaked with black and gray rings, as if they were reaching the center of some atmospheric whirlpool. Out of the mountains, after hours of arduous scrambling, they started across the barren rocky plain.
Before them rose a vast circular structure several stories high, ominously black and without any sign of windows or doors. Above the building protruded two great projections ending in huge, shining discs. One of the monstrous cuplike discs was facing the Sun, the other pointed in the opposite direction.
As the two men came nearer and nearer, the strangeness in the air increased. They felt they were being penetrated through and through with invisible lances, with tiny prickles of heat. "Radiation?" queried Burl softly, afraid of the answer. His father trudged grimly on for a moment, and then put down his pack. He took out a Geiger counter and activated it.
He shook his head. "No radioactivity," he said. "Whatever this is, it isn't that."
They reached the wall of the building. Oddly, here they seemed sheltered from the unusual vibrations. Burl realized that the source was above them, probably the two mighty discs raised high in the sky.