"Look!" said Sarka at last. "There against the sky, beyond and between those two waving tentacles! Note that column of light, scarcely lighter than the light which surrounds it everywhere? It looks like a ma.s.sive column just lighter than everything around it, yet so little lighter that you have to watch closely to see it at all?"

Jaska stared for all of a minute, before she thought back her answer.

"I see it," she said.

"Note now whether it goes, as it reaches outward into s.p.a.ce!"

Jaska followed the mighty height of the thing, outward and outward, and then gasped.

"Sarka," she said, "its end touches the Earth in the very heart of that strange glow we spoke about!"

"Exactly! And people of Earth know nothing about it, because it is invisible to them! It is only from Outside that the glow it makes against the Earth is visible! If we can divert its direction, or render it useless in any way, the Moon will no longer be thrust away by its force!"

A pause of indecision, then Sarka thought again:

"Let us go, Jaska! Keep behind me, right on my heels!"

Slowly, fighting against something that seemed determined to pull, or hurl, them outward from the surface of the Moon with each forward movement they made, they essayed the side of the hill, pausing at the end of what seemed like hours in a sort of hollow just large enough to mask their bodies and stared over its edge into one of the craters of the Moon. Out of the depths of that crater came the discordant sounds, which now were almost deafening, and out of that crater too came the almost invisibly bluish column whose outer tip touched the Earth.

Right before them, so close that they all but rested in its shadow, was one of those monster aircars, its tentacles moving to and fro as though wafted into motion by some vagrant breeze. But since neither Sarka nor Jaska could feel the breeze, Sarka knew that it was life which caused the waving motion of those tentacles of terror.

"Note," he said to Jaska, "that there is a tiny trap-door in the bottom of the aircar, and that the thing rests on a half-dozen of those tentacles!"

"I see," came Jaska's reply.

Jaska went on:

"Note the gleaming thing on the ground, right below the aircar? I wonder what it is?"

They studied the thing there, which seemed to be a huge jewel of some sort that glittered balefully in the eery light of the Moon. It was, perhaps, twice the size of an average man's torso, and was almost exactly cubical in shape. As Sarka studied the thing, he sensed that feeling flowed out of it--that the cube, whatever it was, was alive!

He tore his glance away from it, and realized that he accomplished the feat with a distinct effort of will--as though the cube had willed to hold his gaze, knew he was there. His eyes, peering around the inner slope of the crater--which dipped over, some hundreds of feet down, and plunged downward to some unknown depth--noted a broad, flat stone, off to his right; and around the rim of the crater he counted a full hundred of the aircars, all with their tentacles waving as if they belonged to sentient creatures.

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 a.n.a.lyze 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.

Then, in a trice, it was gone, and a feeling of uneasiness, more compelling than he had ever known before, coursed through the soul of Sarka. Where had the cube gone? What was it? What was its purpose? He tore his eyes away from the spot where he had last seen it, and stared away to the shadow beneath the second nearest aircar, where he had glimpsed another of the cubes.

The cube there, too, was fading out.

"Sarka! Sarka! Look!" came to his brain the thoughts of Jaska.

Sarka turned and stared at her, and a feeling of fear for which he could not account at all took fast hold of him. The eyes of Jaska, wide and staring as they had been when he commanded her to look away from the cube under the aircar, were staring at that flat, table-like rock, off to his right.

There, almost in the center of the rock, a gleaming something was taking shape! Just a dull spot, in the center of the yellow glow; then the beginning of the outline of a cube. Then, all at once, the cube itself, gleaming and baleful!

Sarka gasped in terror. He had seen the cube vanish, its glow disappear, and now here it was, almost close enough to touch, on a rock beside him, gleaming and baleful as before! That it was the same cube he had seen under the first aircar, he somehow knew without being told. That it was a sentient _thing_ he also knew, for now there was no mistaking the fact that, but for the presence in the little hollow of Jaska and Sarka, the cube would not have moved.

Swift as light, Sarka's right hand darted to his belt, where his ray director should be nestled against his need of it. And with his first movement, the cube's brilliance vanished instantly, the cube disappeared, and appeared again right before the face of Sarka, so close he could touch it! Yet he did not turn the ray director against it, nor did he extend his hand to touch the thing--because he was afraid to do so!

Even as the cube appeared before his eyes, thrice baleful and menacing in its close proximity, his eyes darted back to that broad flat rock, where the second gleaming cube now appeared!

"Great G.o.d, Jaska!" he sent mentally, "what does it mean?"

"These," she answered bravely back, "are Moon-soldiers! And, unless we manage not to appear furtive, we are undone!"

Still Sarka made no move, while other gleaming cubes appeared on the flat rock. Five other cubes appeared beside the first, at the rim of the hollow which held the forms of Jaska and Sarka. The cubes were closing on them, oddly like a squad of Earthlings in the olden times, advancing by rushes against an entrenched enemy!

The buzzing sound which they had first heard now seemed accentuated, but, instead of being outside of the listeners, seemed inside them, hammering against their very brains! Messages were being sent to them, or pa.s.sed back and forth between and among the cube-men about them--and they hadn't the slightest idea how to make answer, know whether an answer was expected of them, or what the cube-men thought about them!

Since there was nothing else to do, they lay there, hands clasped, as children in the dark clasp hands, and waited for what might transpire.

Suddenly the discord from the inside of the crater ceased, and all was still, while it came to Sarka that the cube-men who stood before him were in grim communication with something invisible to Sarka and Jaska, somebody, perhaps, deep in the bowels of the Moon, over inside the crater.

They knew, those two, that the cube-soldiers were reporting their presence, and asking instructions; that the Moon had gone silent to listen, and that within a few moments their fate would be decided.

What should they do?

In his hand Sarka held his ray director, with which he knew he could blast one or all of the cubes into nothingness. But still he held his hand, made no move.

Something, however, had to be done, for the discord was starting again, growing in volume. It made Sarka think, oddly enough, of a deaf mute fighting for speech! Then came the first intelligible sound....

A burst, from the depths of the crater, of sardonic laughter!

"Dalis!" said Sarka, and moved. While Sarka moved, Jaska held fast to his arm. Casting her fear to the winds, furious because of the laughter of Dalis, Sarka thrust his ray director back into his belt and stood upright.

Bending over he seized the first of the gleaming cubes and hurled it over the edge of the crater, saw it start plummeting down. But even before it fell out of sight within the crater its gleam had dulled until it was almost impossible to see the thing. Racing as though racing against time, Sarka caught up cube after cube and hurled them all after the first.