Astounding Stories of Super-Science, August 1930

Below each one, as he studied them and strained his eyes to make out details, he caught the baleful gleam of other cubes like the first he had seen. The aircars, it seemed, were either sentinels, at the lip of the crater, or were the dwelling places of sentinels--and the cubes were those sentinels! It seemed absurd, but it came to Sarka in a flash that that was the answer, and his eyes came back to the first cube, because it was nearer and more easy to study. "I will not be swayed by the will of the thing," Sarka told himself. "Nor will I allow it to analyze me! Jaska, do you do likewise!" Beside him, Jaska shivered. He turned to look at her. Her face was coldly white, and her eyes were big with terror and fascination as she stared at that first cube, resting so balefully there under the first aircar. He shook her, and she seemed to bring her eyes to his with a terrific, will-straining effort. "Look at me!" he told her, telepathically. "Keep your eyes on me, for to look at the cube spells danger!" But his own eyes went back to the thing, and he studied it closely. A cold chill raced through his body as he noted that its gleam was becoming dull, fading slowly out. It had gleamed brightly at first, and now was losing its sheen, fading away to invisibility. He thought he should be able, regardless of gleam or color, to see its outline; but its outline, too, seemed to be becoming faint, indistinct.