Jurgens stopped at the top of one high dune and waited for Lansing to catch up. Lansing pulled up beside him, panting with the climb.
“That sounds like thunder up ahead,” said Jurgens. “A heavy storm may be coming up.”
“The color of the sky looks right,” said Lansing, “but it doesn’t look like a storm cloud. I never saw one with an edge that runs straight across. There usually are big thunderheads boiling up, and I see no thunderheads.”
“I thought awhile ago,” Jurgens said, “that I saw a lightning flash, not the bolt itself, but a nicker, like the reflection of a flash.”
“Heat lightning,” Lansing told him. “A reflection against the clouds of lightning far away.”
“In a while we’ll see what it is,” said Jurgens. “Are you ready to go on? Or shall we rest awhile?”
“Go on. I’ll tell you when I need to rest.”
By midafternoon, the great black cloud had climbed well above the horizon. In places it had tinges of deep purple and was, in all, a frightening phenomenon. It appeared to have no motion, no roiling clouds, no wind-driven banks of scudding vapor, although at times it seemed to Lansing, when he stopped for a moment to watch it, to have an almost imperceptible downward movement, as if a thin film of some substance was running down across the blackness, as a thin sheet of water would run down a window-pane during a summer shower. A sense of terrible violence seemed inherent in the cloud itself, the overwhelming threat of heavy weather, and yet there was no visible violence or even threat of violence except for the massive lightning strokes that at intervals ran across the face of darkness. Now the rumble of thunder was continuous.
“Most unusual,” Jurgens said. “I have never seen the like of it.”
“Chaos?” Lansing asked. Asking it, he remembered the chaos, or the sense of chaos (for he doubted now that he’d really seen it) he had glimpsed when he had stood for a moment on the hill of suns above the universe. And that glimpsed chaos, that glimpsed universal chaos had not been anything like this, although he realized that if he were called upon to describe it, he would be unable to tell a single thing about it.
“Perhaps,” said Jurgens. “I ask you: What is Chaos?”
Lansing did not attempt to answer.
They climbed on, and now the way was steeper than it had been at any time since they had started out. They toiled upward over a series of ever higher dunes, and ahead of them the horizon curved away from them to both left and right, as if they were climbing one continuous dune, the rim of which ran in a semicircle, either side of it impinging on the blackness in the sky.
Late in the afternoon they reached the top of the great ridge they had been climbing. Lansing, exhausted, slumped down to the sand, leaning against a large boulder. A large boulder? he asked himself. A boulder here when there had been up to this time nothing larger than a grain of sand? He staggered to his feet, amazed, and the boulder was there — not one boulder, but a clump of them, perched just below the ultimate height of the dune they had been climbing. Resting in the sand, as if someone had, perhaps in ages past, carefully placed them there.
Jurgens stood on top of the dune, straddle-legged, with his crutch dug deep into the sand to prop him up and keep his balance.
To right and left swept the curving edge of the dune that they had climbed, while in front of them the surface broke sharply to plunge downward in an unbroken slope until it reached the bottom of the massive cloud that loomed in front of them.
Looking directly at the cloud, Lansing saw that it was not a cloud, although what it was he did not know. It was a massive wall of utter blackness that rose from where it met the surface of the downward-sloping sand far into the sky, so far that he was forced to crane his neck to see the top of it.
Lightning bolts still slashed across its face with devastating ferocity, and thunder crashed and rumbled. The wall, he saw or thought he saw, was a monstrous dam raised against the sky, and over the lip of it was pouring something that was not water, a gigantic waterfall of a blackness that was not water, crashing down across the face of it, a waterfall so solid and unbroken that he did not see the actual falling of it, but only had the hypnotic sense of its falling. Watching it, he realized that it was not only thunder that he heard, but the deep, awful roar of whatever was falling over the lip of the dam, the Niagara-like rushing sound of something falling from great height, falling from the unknown into the unknown. It seemed to him that the very ground beneath him was trembling with the roar.
He turned his head and looked at Jurgens, but the robot did not notice him. He was leaning heavily upon his crutch, staring at the blackness, seemingly entranced and hypnotized by it, rigid with his watching.
Lansing shifted his gaze back to the blackness and now, clearer than ever, it seemed to be a dam, although a moment later he was not sure it was a dam. First a cloud and then a dam and now, he wondered, what could it be now?
One thing he knew — it was not the answer that they sought or even a clue that in time might provide the answer. Like the cube and doors, like the installation and the singing tower, it was meaningless. Perhaps not meaningless entirely, but meaningless to him and Jurgens and the other humans, to the intelligence and perception that resided in the human mind.
“The end of the world,” said Jurgens, speaking with a strange catch in his voice.
“The end of this world?” asked Lansing, and having said it, was sorry that he had, for it was a silly thing to say. Why he had said it, he could not imagine.
“Perhaps not only of this world,” said Jurgens. “Not of this world alone. The end of all worlds. The end of everything. There goes the universe. Eaten by a blackness.”
The robot moved forward a step, lifting his crutch and probing for a solid place to set it. He did not find a solid place. The crutch skidded and went flying from his hand. The bad leg collapsed under him and sent him lurching forward. He fell and somersaulted on the slope. His pack came off his shoulders and went skidding down the slope before him. Jurgens’s hands were working frantically, clawing at the slope to stop his slide, but there was nothing he could grasp. There was only sand to grasp and it was sliding all about him, sliding with him. His clutching hands left long print marks in the sand.
Lansing, who had been crouching, came swiftly to his feet. If he could remain upright, he thought, driving his feet deep into the sand beneath the sliding surface, there would be a chance to reach Jurgens and halt his slide, drag him back to safety.
He took a downward step and his forward-reaching foot found no solid footing. The sand was like so much powder. There was no walking on it, no standing on it. He tried to throw himself backward, stretching desperately to reach the top of the dune, hoping to use it to lever himself off the moving surface. But his foot was slipping faster now, plowing a deep furrow in the sand, and he came down on the face of the slope and slid, slowly, ever so slowly, but with no hope of stopping. Not only was he sliding, but all the sand about him made a slow but inexorable response to the pull of gravity.
He thrust out his legs and arms to present a wider resistance to the surface on which he slid, and it seemed, when he did so, that he might be moving just a bit more slowly, although it was hard to tell. It was hopeless, he told himself, being honest with himself. Any effort on his part to claw his way upward would do no more than disturb the sand, making it slide the faster, carrying him with it.
But now he knew that the downward movement had slowed somewhat and for a moment it seemed that the slide had stopped. He lay spread-eagled on the sand, fearful of moving, apprehensive that any movement on his part would start the slide again.