It is a sea, though they call it sand.

They call it sand because it is still and red and dense with grains. They call it sand because the thin wind whips it, and whirls its dusty skim away to the tight horizons of Mars.

But only a sea could so brood with the memory of aeons. Only a sea, lying so silent beneath the high skies, could hint the mystery of life still behind its barren veil.

To practical, rational man, it is the Xanthe Desert. Whatever else he might unwittingly be, S. Nuwell Eli considered himself a practical, rational man, and it was across the bumpy sands of the Xanthe Desert that he guided his groundcar westward with that somewhat cautious proficiency that mistrusts its own mastery of the machine. Maya Cara Nome, his colleague in this mission to which he had addressed himself, was a silent companion.

Nuwell's liquid brown eyes, insistent upon their visual clarity, saw the red sand as the blowing surface of unliving solidity. Only clarity was admitted to Nuwell, and the only living clarity was man and beast and vegetation, spotted in the dome cities and dome farms of the lowlands. He and Maya scurried, transiting sparks of the only life, insecure and hastening in the absence of the net of roads which eventually would bind the Martian surface to human reality from the toeholds of the dome cities.

In that opposite world which was the other side of the groundcar's seat, Maya Cara Nome's opaque black eyes struggled against the surface. They struggled not from any rational motivation but from long stubbornness, from habit, as a fly kicks six-legged and constant against the surface tension of a trapping pool.

Formally, Maya was allied to Newell's clarity and solidity, and she could express this alliance with complete logic if called on. But behind the casually blowing sand she sensed a depth. The shimmering atmosphere, hostile to man, which sealed the red desert was a lens that distorted and concealed by its intervention. The groundcar was a mechanical bug, an alienness with which timorous man had allied himself; allied with it against reality, she and Nuwell were hastened by it through reality, unseeing, toward the goal of a more comfortable unreality.

The groundcar bumped and slithered, and an orange dust-cloud boiled up from its broad tires and wafted away across the sculpted sand. The desert stretched away, silent and empty, to the distant horizon; the groundcar the only humming disturbance of its silence and emptiness. The steel-blue sky shimmered above, a lens capping the red surface.

The groundcar rolled westward, slashing toward its goal from the distant lowland of Solis Lacus. Far away, two men, machineless, plodded this same Xanthe Desert toward the same goal; but they plodded southward, approaching on a different radius.

They were naked. In a thin atmosphere without sufficient oxygen to support animal life or even the higher forms of terrestrial plant life, they wore no marsuits, no helmets, no oxygen tanks.

The man who walked in front was tall, erect, powerfully muscled. His features and short-clipped hair were coarse, but self-assured intelligence shone in his smoky eyes. He moved across the loose sand, barefoot, with easy grace.

The—man?—that shambled behind him was as tall, but appeared shorter and even more muscular because his shoulders and head were hunched forward. His even coarser face was characterized by vacuously slack mouth and blue eyes empty of any expression except an occasional brief frown of puzzlement.

Toward a focal point: from the east, two people; from the north, two people. If in the efficient self-assurance of Adam Hennessey could be paralleled a variant harmony with the insistent surfaceness of S. Nuwell Eli, does any coincidental parallelism exist between Brute Hennessey and Maya Cara Nome?

Puzzlement was the climate of Brute's mind. This surface film of things through which he ploughed his way, the swarming currents below the surface—all were chaos. He grasped vaguely at comprehension without achieving, the effective coalescence of electric ideas always falling short before reaching consciousness.

The two men plodded, naked, through the loose sand. Above them in the Mars-blue dome of day, the weak sun turned downward, warning of its eventual departure.

A two-passengered groundcar and two men, widely apart, and yet bound for the same destination....

The destination was a lone, sprawling building in the desert. It could have been a huge warehouse, or a fortress, of black, almost windowless Martian stone. The only outstanding feature of its virtually featureless hulk was a tower which struck upward from its northern side.

As the summer afternoon progressed, Dr. G. O. T. Hennessey paced the windy summit of the tower, peered frequently into the desert north beneath a sunshading hand, and waggled his goat beard in annoyance under his transparent marshelmet.

Had the helmet speaker been on or the air less thin, one might have determined that Goat Hennessey was utilizing some choice profanity, directed at those two absent personages whose names were, respectively, Adam and Brute.

The airlock to the tower elevator opened and a small creature—a child?—emerged onto the roof. Distorted, humpbacked and barrel-chested, it scuttled on reed-thin legs to Goat's side. It wore no marsuit.

"Father!" screeched this apparition, its thin voice curiously muffled by the tenuous air. "Petway fell in the laundry vat!"

"For the love of space!" muttered Goat in exasperation. "Is there water in it?"

When the newcomer gave no sign of hearing, Goat realized his helmet speaker was off. He switched it on.

"Is there water in the vat?" he repeated.

"Yes, sir. It's full of suds and clothes."

"Well, go fish him out before he soaks up all the water. The soap will make him sick."

The messenger turned, almost tripping over its own broad feet, and went back through the airlock. Goat returned to his northward vigil.

Miles away, Nuwell slowed the groundcar as it approached the lip of that precipitous slope bordering the short canal which connects Juventae Fons with the Arorae Sinus Lowland. He consulted a rough chart, and turned the groundcar southward. A drive of about a kilometer brought them to a wide descending ledge down which they were able to drive into the canal.

Here, on the flat lowland surface, the canal sage grew thick, a gray-green expanse stretching unbroken to the distant cliff that was the other side of the canal. Occasionally above its smoothness thrust the giant barrel of a canal cactus.

Nuwell headed the groundcar straight across the canal, for the chart showed that the nearest upward ledge on the other side was conveniently almost opposite. The big wheels bent and crushed the canal sage, leaving a double trail.

The canal sage brought with it the comforting feeling of surface life once more. This feeling, for no reason that he could have determined consciously, released Nuwell's tongue.

"Maya," he said, in a voice that betrayed determination behind its mildness, "I don't see any real reason for waiting. When we've cleared up this matter at Ultra Vires and get back to Mars City, I think we should get married."

She glanced at his handsome profile and smiled affectionately.

"I'm complimented by your impatience, Nuwell," she said. "But there is a good reason for waiting, for me. When we're married, I want to be your wife, completely. I want to keep your home and mother your children. Don't you understand that?"

"That's what I want, too," he said. "That's my idea of what marriage is. But, Maya, if you insist on finishing this government assignment, that could be a long time off."

"I know, and I don't like it any better than you do, darling," said Maya. "But it's cost the Earth government a great deal of trouble and money to send me here, and you know how long it would take for them to get a replacement to Mars for me. I don't feel that I can let them down, and I don't think it would be much of a beginning to our marriage for me to be running around ferreting out rebels during the first months of it."

"That's another thing I don't like, Maya," said Nuwell. "It's dangerous, and I don't want anything to happen to you."

"It's your work, too, and it's not absolutely safe for you, either. I'll be sharing it with you when we're married, and for you it will go on for a long time. I have a specific mission here, to locate the rebel headquarters, and as soon as I've done that I'll be more than happy to become just a contented housewife and leave the rest of it to you."

Nuwell shrugged, a little disconsolately, and turned his attention to the task of negotiating the groundcar up the ascending slope.

She was a strange creature, this little Maya of his. She had been born on Mars and, orphaned by some unknown disaster, had been cared for during her first years by the mysterious, grotesque native Martians. When they took her at last to one of the dome cities, she was sent to Earth for rearing. And now she was back on Mars as an undercover agent of the Earth government, seeking to ferret out the rebels known to be engaging in widespread forbidden activities.

Often he did not understand her, but he wanted her, nevertheless.

Nuwell steered the groundcar slowly up the slope, over rubble and ruts, avoiding the largest rocks. At last they reached the top, and the groundcar arrowed out over the desert again, picking up speed.

Far to the left and ahead of them there was another dust-cloud drifting up, one that was not of the thin wind, but nearly stationary. Nuwell found the binoculars in the storage compartment and handed them to Maya.

"What's that over there?" he wondered. "Another groundcar? Take a look, Maya."

Maya trained the glasses in the direction indicated, through the groundcar's transparent dome. It was difficult to get them focused, for the groundcar swayed and jolted, but at last she was able to make brief identification.

"They're Martians, Nuwell," she said. "Can we drive over that way?"

"You've seen Martians before," he said.

"But I'd like to speak with them," she said. "I talk their language, you know."

"Yes, I do know, darling, but that's utterly foolish. They're only animals, after all, and we have to get to Ultra Vires before night, if we can."

He kept the groundcar on its course.

Maya lapsed into disgruntled silence. Nuwell stole a sidelong glance at her, his breath catching slightly at the curve of the petite, perfectly feminine form beneath the loose Martian tunic and baggy trousers. He reached over and patted her hand.

But Maya was offended. She kept her black head turned away from him, looking out of the groundcar dome across the desert.

At their destination, Goat Hennessey peered eagerly into the distance, searching.

This time, his watery blue eyes picked up two tiny figures on the horizon. He watched them as they approached, finally detailing themselves into two naked, pink creatures of manshape and only slightly more than mansize.

"They made it," he muttered. "Both of them. Good!"

He turned and entered the airlock. As soon as its air reached terrestrial density and composition, he removed his marshelmet.

Goat rode the elevator to the ground level, left it and hurried down a corridor, reaching the outside airlock in time to admit the two figures.

Adam entered first, easily confident, carrying his head like a king. Brute shambled behind him.

"Everything go all right?" asked Goat, his voice quavering in his anxiety.

"Fine, father," said Adam, smiling to reveal savage, even teeth.

"Nothing unusual happen?"

"Nothing at all, sir."

"You forget, Adam?" mouthed Brute eagerly. "You forget you fall?"

Adam spun on him ferociously, raising a heavy hand in threat. Brute did not cringe.

"I forget nothing!" snarled Adam. "You crazy Brute, I say it is nothing!"

"But, Adam—"

"I say it is nothing!" howled Adam and sprang for him.

"Stop it!" snapped Goat, like the crack of a whip, and they froze in the moment of their grappling. Sheepishly, they parted and stood side by side before him.

"I'll listen to details after supper," said Goat. "The children are hungry, and so am I."

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