into the atmosphere of the planet he cut the rear propulsion rockets of his slim single-seater and prepared to land. He sighted the base's small cluster of buildings and the mooring tower in his fore visi-screen and he made quick rapid adjustments on his instrument panel as his slender ship slanted toward them in a screaming dive....

When the nose of his ship made contact with a mooring socket, he set all instruments at zero. He climbed to his feet and stretched wearily. Then he walked to the sliding side door of the ship, released the air lock and stepped out onto the ramp that flanked the mooring tower.

From this position, some two hundred feet above the ground, he had his first look at the terrain of Mars. Great gray wastelands spread endlessly in all four directions and the only break in this monotony was a low ridge of hills on the far-distant eastern horizon.

Ward shivered slightly. He hadn't been prepared for anything this depressing. The small group of squat buildings beneath him looked like tiny objects adrift in a vast, terrible gray sea.

A man appeared at the door of the central building and Ward felt an idiotic sensation of relief at the sight of a human, moving figure in that dead, silent, gray terrain.

The man waved to Ward and walked from the doorway toward the base of the mooring tower.

Ward descended to the ground in the small cage of the tower elevator. He stepped out onto the soft, flaky soil of Mars as the man he had seen from above came up to the tower.

"Lieutenant Harrison reporting for duty, sir," he said. He saluted and noticed with a certain satisfaction the other's embarrassment at this military recognition which he didn't deserve.

"My name is Halliday," the man said, after a short awkward pause. He extended his hand. "I'm certainly glad to have you here, Lieutenant."

As Ward shook hands, he appraised the man carefully, and found nothing in his examination to change his previously acquired opinion.

Thomas Halliday was small and stooped, with sallow features and nervously shifting eyes, which looked startlingly large behind thick strong glasses. His hair was thin and faded brown in color. There was a peculiar tight look about his mouth and jaw, as if he were in a continual state of faint exasperation.

This, thought Ward, was the man who had been holding up the development of this area for three years. And, looking at him, it was easy to see why.

Ward had his bag in his hand. Halliday, noticing it, asked, "Did you bring any arms with you?"

Ward patted the raytube in the smart military holster at his hip.

"Just this," he said. He added drily, "Expecting trouble?"

"No," Halliday answered. His eyes shifted from Ward's and swept about in a long inspection of the vast, sprawling, deserted terrain that stretched away on all four sides like a boundless ocean.

"But," he added, "it's when you're not expecting trouble that you're most likely to run into it."

Ward smiled to himself as he followed Halliday's thin stooped figure to the main building, a squat solid structure of heavy duralloy steel, with only one door and no windows at all.

The man was obviously a neurotic mass of nerves, or else he was indulging in a bit of melodrama to impress his new assistant.

Halliday stepped aside at the door and Ward preceded him into the hot, sparsely furnished room. Halliday followed him, closing the door behind him and setting the mechanism of a powerful automatic lock before turning to Ward with an apologetic little smile.

"You'll find it rather cramped at first," he said. "I'll sleep out here and you can use the storeroom as a bedroom. That's all the living quarters we have, excepting the kitchen, but I'm sure we'll manage."

Ward set his grip down and glanced about at the chart-covered walls, the plain, badly scuffed furniture and he was not particularly enthused at the prospect of being cooped up in this hot little oven of a room with Halliday.

"What about the other buildings?" he asked. "Surely there'd be room there for me to bunk."

"We use those building for equipment," Halliday said. "And besides, this building is safer."

Ward glanced at the little man with a faint, ironic smile.

"Is there something here to be afraid of?" His tone was blandly polite, but he could not completely conceal an undercurrent of contempt.

"I don't mean to alarm you, Lieutenant," Halliday said, "but this area of Mars is not quite the safest place in the universe." He removed his thick glasses with a nervous little gesture and smiled uncertainly at Ward. "I really think it wiser for you to sleep here."

"Unless that's an order," Ward said, "I'd rather sleep in comfort in one of the other buildings and take my chances on your bogy-men catching me."

Halliday replaced his glasses. He was no longer smiling.

"I'm afraid, Lieutenant, you must consider it as an order."

He turned slowly and re-checked the huge gleaming lock on the door, then walked to a littered, dusty desk in one corner of the room and sat down. It was obvious that the discussion was ended.

Ward shrugged and carried his grip into a small windowless storeroom that was directly off the main room of the small structure. There were bales of supplies, a cot and a stool. A vague musty odor permeated the air. He tossed his grip onto the cot, stripped off his tunic and walked back into the room where Halliday was seated at his desk.

Halliday looked up with a smile and removed his glasses with a characteristic nervous movement of his thin hands.

"Not exactly the choicest accommodations, eh?" he said, in an attempt at heartiness, which struck Ward as being almost pathetic.

"I'll get by," Ward said. He loosened the collar of his shirt and glanced at the massive steel door, closed and tightly locked. "Any objection to letting in a little air?" he asked. "It's pretty close in here."

Halliday smiled and his eyes flicked to the closed door. He put his glasses on again and spent quite a time adjusting them to his thin nose.

"I'm afraid we'll have to put up with the closeness," he said.

Ward sighed and sat down in a chair facing Halliday.

"You're afraid of something," he said bluntly. "Supposing you tell me about it."

"As a matter of fact, I was meaning to," Halliday said. "You see, on this section we're pretty well isolated from the rest of the Earth stations on Mars. We receive all supplies and mail by a direct materialization unit. No space craft puts in here. We're here all alone and if anything happened to us all the data and work that has been compiled might be lost."

As Halliday removed his glasses again with a quick aimless gesture, Ward thought, "A lot you care about the records and data. It's your skin you want to save."

Halliday coughed and replaced his glasses.

"This area is inhabited by a species of creature which I do not believe has been classified. I do not know if they are human or if they possess intelligence. I do not even know if they are 'alive' in the sense that we speak of life. Possibly their energy is of electrical or carboniferous origin, or it could be even vegetable in nature. As you see I know little enough about these neighbors of ours, but I do know that they are dangerous. They resent the work that is being done here." Halliday frowned and twisted a pencil in his hands. "I'm not even sure of that. Possibly they are without rational motivation at all. It may be that they are merely moved to action by the sight of another object in motion. But whatever their reason, they have been very troublesome. That, really, is all I know about them. And that is the reason that I exercise such care. I have a small periscope installed on the roof and before I unlock the door I study the entire surrounding terrain to be sure there are no Raspers in sight."

"Why do you call them Raspers?" Ward asked.

"Because of a peculiar sound that seems to emanate from