It was nine o'clock at night when Lockley killed the porcupine, and ten by the time Jill had gone back to sleep huddled between the projecting roots of a giant tree. Shortly after midnight Lockley had been awakened when a skunk defeated a hungry predator within a hundred yards of their bivouac. But some time in between, there was another happening of much greater importance elsewhere.

Something came out of Boulder Lake National Park. All humans had supposedly fled from it. It was abandoned to the creatures of the thing from the sky. But something came out of it.

Nobody saw the thing, of course. Nobody could approach it, which was the point immediately demonstrated. No human being could endure being within seven miles of whatever it was. It was evidently a vehicle of some sort, however, because it swung terror beams before it, and terror beams on either side, and when it was clear of the Park it played terror beams behind it, too. Men who suffered the lightest touch of those sweeping beams of terror and anguish moved frantically to avoid having the experience again. So when something moved out of the Park and sent wavering terror beams before it, men moved to one side or the other and gave it room.

On a large-scale map in the military area command post, its progress could be watched as it was reported. The reports described a development of unbearable beam strength which showed up as a bulge in the cordon's roughly circular line. That bulge, which was the cordon itself moving back, moved outward and became a half-circle some miles across. It continued to move outward, and on the map it appeared like a pseudopod extruded by an enormous amoeba. It was the area of effectiveness of a weapon previously unknown on earth—the area where humans could not stay.

Deliberately, the unseen moving thing severed itself from the similar and larger weapon field which was its birthplace and its home. It moved with great deliberation toward the small town of Maplewood, twenty miles from the border of the Park.

Jeeps and motorcycles scurried ahead of it, just out of reach of its beams. They made sure that houses and farms and all inhabited places were emptied of people before the moving terror beams could engulf them. They went into the town of Maplewood itself and frantically made sure that nothing alive remained in it. They went on to clear the countryside beyond.

The unseen thing from the Park moved onward. High overhead there was a dull muttering like faraway thunder, but it was planes with filled bomb racks circling above the starlit land. There were men in those planes who ached to dive down and destroy this separated fraction of an invasion. But there were firm orders from the Pentagon. So long as the invaders killed nobody, they were not to be attacked. There was reason for the order in the desire of the government to be on friendly terms with a race which could travel between the stars. But there was an even more urgent reason. The aliens had not yet begun to murder, but it was suspected that they had a horrifying power to kill. So it was firmly commanded that no bomb or missile or bullet was to be used unless the invaders invited hostilities by killing humans. Their captives—the crew of a helicopter—might be freed if aliens and men achieved friendship. So for now—no provocation!

The thing which nobody saw moved comfortably over the ground between the park and Maplewood. In the center of the weapon field there was a something which generated the terror beam and probably carried passengers. Whatever it was, it moved onward and into Maplewood and for seven miles in every direction troops watched for it to move out again. Artillerymen had guns ready to fire upon it if they ever got firing coordinates and permission to go into action. Planes were ready to drop bombs if they ever got leave to do so. And a few miles away there were rockets ready to prove their accuracy and devastating capacity if only given a launching command. But nothing happened. Not even a flare was permitted to be dropped by the planes far up in the sky. A flare might be taken for hostility.

The thing from the Park stayed in Maplewood for two hours. At the end of that time it moved deliberately back toward the Park. It left the town untouched save for certain curious burglaries of hardware stores and radio shops and a garage or two. It looked as if intensely curious not-human beings had moved from their redoubt—Boulder Lake—to find out what civilization human beings had attained. They could guess at it by the buildings and the homes, but most notably in the technical shops of the inhabitants.

It went slowly and deliberately back into the Park. Humans moved cautiously back into the area that had been emptied. Not many, but enough to be sure that the thing had really returned to the place from which it had come. Soldiers were tentatively entering the again-abandoned town of Maplewood when the unseen thing changed the range of its weapon bearing on that little city. It was then presumably not less than seven miles on its way back to Boulder Lake. The military had congratulated themselves on what they'd learned. The beam projectors at the lake had a range of much more than seven miles, but this movable, unidentifiable thing carried a lesser armament. From it, men and animals seven miles away were safe. This was notable news.

Then the unseen object did something. The terror beam that flicked back and forth doubled in intensity. The soldiers just reentering Maplewood smelled foulness and saw bright lights. Bellowings deafened them. They fell with every muscle rigid in spasm. Beyond them other men were paralyzed. For five minutes the invaders' mobile weapon paralyzed all living things for a distance of fifteen miles. Then for thirty seconds it paralyzed living things for a distance of thirty miles. For a bare instant it convulsed men and animals for a greater distance yet. And all these victims of the terror beam knew, thereafter, an invincible horror of the beam.

The thing from the Park which nobody had seen went back into the Park. And then men were permitted to return to exactly the same places they'd been allowed to occupy before the thing began its excursion.

It seemed that nothing was changed, but everything was changed. If there were mobile carriers of the invasion weapon, then victory could not be had by a single atom bomb fired into Boulder Lake. There might be a dozen separate mobile terror beam generators scattered through the Park. Any atomic attack would need to be multiplied in its violence to be certain of results. Instead of one bomb there might be a need for fifty. They would have to destroy the Park utterly, even its mountains. And the fallout from so many atom bombs simply could not be risked. The invaders were effectively invulnerable.

While this undesirable situation was being demonstrated, Jill slept heavily between two roots of a very large tree, and Lockley dozed against a nearby tree trunk. He believed that he guarded Jill most vigilantly.

He awoke at dawn with the din of bird song in his ears. Jill opened her eyes at almost the same instant. She smiled at him and tried to get up. She was stiff and sore from the hardness of the ground on which she'd slept. But it was a new day, and there was breakfast. It was porcupine cooked the night before.

"Somehow," said Jill as she nibbled at a bone, "somehow I feel more cheerful than I did."

"That's a mistake," Lockley told her. "Start out with a few premonitions and the day improves as they turn out wrong. But if you start out hoping, the day ends miserably with most of your hopes denied."

"You've got premonitions?" she asked.

"Definitely," he said.

It was true. As yet he knew nothing of last night's temporary occupation of a human town, but he believed he knew how the terror beam worked even if he couldn't figure out a way to generate it. He could imagine no defense against it. But if Jill had awakened feeling cheerful, there was no reason to depress her. She'd have reason enough to be dejected later, beginning with proof of Vale's death and going on from there.

"We might listen to the news," she suggested. "A premonition or two might be ruled out right away!"

Silently, he turned on the little radio. Automatically, he set it for the lowest volume they could hear distinctly.

The main item in the news was a baldly factual but toned-down report of the thing from the lake which had left the park and examined a small human town in detail and then had returned to the Park. There were reports of peculiar hoofprints found where the invaders had been. They were not the hoofprints of any earthly animal. There was an optimistic report from the scientists at work on the problem of the beam. Someone had come up with an idea and some calculations which seemed to promise that the beam would presently be duplicated. Once it was duplicated, of course a way to neutralize it could be found.

Lockley grunted. The broadcast was enthusiastic in its comments on the scientists. It talked gobbledegook which sounded as if it meant something but was actually nonsense. It barely touched on the fact that human beings were now ordered out of a much larger space than had been evacuated before. There was a statement from an important official that panic buying of food was both unnecessary and unwise. Lockley grunted again when the newscast ended.

"The idea that anything that can be duplicated can be canceled," he announced gloomily, "is unfortunately rot. We can duplicate sounds, but there's no way to make them cancel out! Not accurately!"

Jill had eaten a substantial part of the porcupine while the newscast was on. It was not a satisfying breakfast, but it cheered her immensely after two days of near-starvation.

"But," she observed, "maybe that won't apply to this business when you report what you know. It's not likely that anybody else has stood just outside a beam and made tests of what it's like and how it's aimed and so on."

They started off. For journeying in the Park, Lockley had the advantage that as part of the preparation for making a new map, he'd familiarized himself with all mapping done to date. He knew very nearly where he was. He knew within a close margin just where the terror beam stretched. He'd smashed his watch, which during sunshine substituted admirably for a compass, but he could maintain a reasonably straight line toward that part of the Park's border the terror beam would cross.

They moved doggedly over mountain-flanks and up valleys, and once they followed a winding hollow for a long way because it led toward their destination without demanding that they climb. It was in this area that, pushing through brushwood beside a running stream, they came abruptly upon a big brown bear. He was no more than a hundred feet away. He stared at them inquisitively, raising his nose to sniff for their scent.

Lockley bent and picked up a stone. He threw it. It clattered on rocks on the ground. The bear made a whuffing sound and moved aggrievedly away.

"I'd have been afraid to do that," said Jill.

"It was a he-bear," said Lockley. "I wouldn't have tried it on a she-bear with cubs."

They went on and on. At mid-morning Lockley found some mushrooms. They were insipid and only acute hunger would make them edible raw, but he filled his pockets. A little later there were berries, and as they gathered and ate them he lectured learnedly on edible wild plants to be found in the wilderness. Jill listened with apparent interest. When they left the berry patch they swung to the left to avoid a steep climb directly in their way. And suddenly Lockley stopped short. At the same instant Jill caught at his arm. She'd turned white.

They turned and ran.

A hundred yards back, Lockley slackened his speed. They stopped. After a moment he managed to grin mirthlessly.

"A conditioned reflex," he said wryly. "We smell something and we run. But I think it's the old familiar terror beam that crosses highways to stop men from using them. If it were a portable beam projector with somebody aiming it, we wouldn't be talking about it."

Jill panted, partly with relief.

"I've thought of something I want to try," said Lockley. "I should have tried it yesterday when I first smashed my watch."

He retraced his steps to the spot where they'd caught the first whiff of that disgusting reptilian-jungle-decay odor which had bombarded their nostrils. Jill called anxiously, "Be careful!"

He nodded. He got the coiled bronze watchspring out of his pocket. He went very cautiously to the spot where the smell became noticeable. Standing well back from it, he tossed one end of the spring into it. He drew it back. He repeated the operation. He moved to one side. Again he swung the gold-colored ribbon. He dangled it back and forth. Then he drew back yet again and wrapped his left hand and wrists with many turns of the thin bronze spring, carefully spacing the turns. He moved forward once more.

He came back, his expression showing no elation at all.

"No good," he said unhappily. "In a way, it works. The spring acts as an aerial and picks up more of the beam than my hand. But I tried to make a Faraday cage. That will stop most electromagnetic radiation, but not this stuff! It goes right through, like electrons through a radio tube grid."

He put the spring back in his pocket.

"Well," he grimaced. "Let's go on again. I had a little bit of hope, but some smarter men than I am haven't got the right gimmick yet."

They started off once more. And this time they did not choose a path for easier travel, but went up a steep slope that rose for hundreds of feet to arrive at a crest with another steep slope going downhill. At the top Lockley said sourly, "I did discover one thing, if it means anything. The beam leaks at its edges, but it's only leakage. It doesn't diffuse. It's tight. It's more like a searchlight beam than anything else in that way. You can see a light beam at night because dust motes scatter some part of it. But most of the light goes straight on. This stuff does the same. It's hard to imagine a limit to its range."

He trudged on downhill. Jill followed him. Presently, when they'd covered two miles or more with no lightening of his expression, she said, "You said you understand how it works. Radio and radar beams don't have effects like this. How does this have them?"

"It makes high frequency currents on the surface of anything it hits. High frequency doesn't go into flesh or metal. It travels on the surface only. So when this beam hits a man it generates high frequency on his skin. That induces counter currents underneath, and they stimulate all the sensory nerves we've got—of our eyes and ears and noses as well as our skin. Every nerve reports its own kind of sensation. Run current over your tongue, and you taste. Induce a current in your eyes, and you see flashes of light. So the beam makes all our senses report everything they're capable of reporting, true or not, and we're blinded and deafened. Then the nerves to our muscles report to them that they're to contract, and they do. So we're paralyzed."

"And," said Jill, "if there's a way to generate high frequency on a man's skin there's nothing that can be done?"

"Nothing," said Lockley dourly.

"Maybe," said Jill, "you can figure out a way to prevent that high frequency generation."

He shrugged. Jill frowned as she followed him. She hadn't forgotten Vale, but she owed some gratitude to Lockley. Womanlike, she tried to pay part of it by urging him to do something he considered impossible.

"At least," she suggested, "it can't be a death ray!"

Lockley looked at her.

"You're wrong there," he said coldly. "It can."

Jill frowned again. Not because of his statement, but because she hadn't succeeded in diverting his mind from gloomy things. She had reason enough for sadness, herself. If she spoke of it, Lockley would try to encourage her. But he was concerned with more than his own emotions. Without really knowing it, Jill had come to feel a great confidence in Lockley. It had been reassuring that he could find food, and perhaps more reassuring that he could chase away a bear. Such talents were not logical reasons for being confident that he could solve the alien's seemingly invincible weapon, but she was inclined to feel so. And if she could encourage him to cope with the monsters—why—it would be even a form of loyalty to Vale. So she believed.

In the late afternoon Lockley said, "Another four or five miles and we ought to be out of the Park and on another highway we'll hope won't be blocked by a terror beam. Anyhow there should be an occasional farmhouse where we can find some sort of civilized food."

Jill said hungrily, "Scrambled eggs!"

"Probably," he agreed.

They went on and on. Three miles. Four. Five. Five and a half. They descended a minor slope and came to a hard-surfaced road with tire marks on it and a sign sternly urging care in driving. There were ploughed fields in which crops were growing. There was a row of stubby telephone poles with a sagging wire between them.

"We'll head west," said Lockley. "There ought to be a farmhouse somewhere near."

"And people," said Jill. "I look terrible!"

He regarded her with approval.

"No. You look all right. You look fine!"

It was pleasing that he seemed to mean it. But immediately she said, "Maybe we'll be able to find out about ... about...."

"Vale," agreed Lockley. "But don't be disappointed if we don't. He could have escaped or been freed without everybody knowing it."

She said in surprise, "Been freed! That's something I didn't think of. He'd set to work to make them understand that we humans are intelligent and they ought to make friends with us. That would be the first thing he'd think of. And they might set him free to arrange it."

Lockley said, "Yes," in a carefully noncommittal tone.

Another mile, this time on the hard road. It seemed strange to walk on so unyielding a surface after so many miles on quite different kinds of footing. It was almost sunset now. There was a farmhouse set well back from the road and barely discernable beyond nearby growing corn. The house seemed dead. It was neat enough and in good repair. There were clackings of chickens from somewhere behind it. But it had the feel of emptiness.

Lockley called. He called again. He went to the door and would have called once more, but the door opened at a touch.

"Evacuated," he said. "Did you notice that there was a telephone line leading here from the road?"

He hunted in the now shadowy rooms. He found the telephone. He lifted the receiver and heard the humming of the line. He tried to call an operator. He heard the muted buzz that said the call was sounding. But there was no answer. He found a telephone book and dialed one number after another. Sheriff. Preacher. Doctor. Garage. Operator again. General store.... He could tell that telephones rang dutifully in remote abandoned places. But there was no answer at all.

"I'll look in the chicken coops," said Jill practically.

She came back with eggs. She said briefly, "The chickens were hungry. I fed them and left the chicken yard gate open. I wonder if the beam hurts them too?"

"It does," said Lockley.

He made a light and then a fire and she cooked eggs which belonged to the unknown people who owned this house and who had walked out of it when instructions for immediate evacuation came. They felt queer, making free with this house of a stranger. They felt that he might come in and be indignant with them.

"I ought to wash the dishes," said Jill when they were finished.

"No," said Lockley. "We go on. We need to find some soldiers, or a telephone that works...."

"I'm not a good dishwasher anyhow," said Jill guiltily.

Lockley put a banknote on the kitchen table, with a weight on it to keep it from blowing away. They closed the house door. They'd eaten fully and luxuriously of eggs and partly stale bread and the sensation was admirable. They went out to the highway again.

"West is still our best bet," said Lockley. "They've blocked the highway to eastward with that terror beam."

The sun had set now, but a fading glory remained in the sky. They saw the slenderest, barest crescent of a new moon practically hidden in the sunset glow. They walked upon a civilized road, with a fence on one side of it and above it a single sagging telephone wire that could be made out against the stars.

"I feel," said Jill, "as if we were almost safe, now. All this looks so ordinary and reassuring."

"But we'd better keep our noses alert," Lockley told her. "We know that one beam comes nearly this far and probably—no, certainly crosses this road. There may be more."

"Oh, yes," agreed Jill. Then she said irrelevantly, "I'll bet they do make him a sort of—ambassador to our government to arrange for making friends. He'll be able to convince them!"

Again she referred to Vale. Lockley said nothing.

Night was now fully fallen. There were myriad stars overhead. They saw the telephone wire dipping between poles against the sky's brightness. They passed an open gate where another telephone wire led away, doubtless to another farmhouse. But if there was no one at the other end of a telephone line, there was no point in using a phone.

There came a rumbling noise behind them. They stared at one another in the starlight. The rumbling approached.

"It—can't be!" said Jill, marvelling.

"It's a motor," said Lockley. He could not feel complete relief. "Sounds like a truck. I wonder—"

He felt uneasiness. But it was absurd. Only human beings would use motor trucks.

There was a glow in the distance behind them. It came nearer as the sound of the motor approached. The motor's mutter became a grumble. It was definitely a truck. They could hear those other sounds that trucks always make in addition to their motor noises.

It came up to the curve they'd rounded last. Its headlight beams glared on the cornstalks growing next to the highway. One headlight appeared around the turn. Then the other. An enormous trailer-truck combination came bumbling toward them. Jill held up her hand for it to stop. Its headlights shone brightly upon her.

Airbrakes came on. The giant combination—cab in front, gigantic box body behind—came to a halt. A man leaned out. He said amazedly, "Hey, what are you folks doin' here? Everybody's supposed to be long gone! Ain't you heard about all civilians clearing out from twenty miles outside the Park? There's boogers in there! Characters from Mars or somewhere. They eat people!"

Even in the starlight Lockley saw the familiar Wild Life Control markings on the trailer. He heard Jill, her voice shaking with relief, explaining that she'd been at the construction camp and had been left behind, and that she and Lockley had made their way out.

"We want to get to a telephone," she added. "He has some information he wants to give to the Army. It's very important." Then she swallowed. "And I'd like to ask if you've heard anything about a Mr. Vale. He was taken prisoner by the creatures up there. Have you heard of his being released?"

The driver hesitated. Then he said, "No, ma'm. Not a word about him. But we'll take care of you two! You musta been through plenty! Jud, you go get in the trailer, back yonder. Make room for these two folks up on the front seat." He added explanatorily, "There's cases and stuff in the back, ma'm. You two folks climb right up here alongside of me. You sure musta had a time!"

The door on the near side of the truck cab opened. A small man got out. Silently, he went to the rear of the trailer and swung up out of sight. Jill climbed into the opened door. Lockley followed her. He still felt an irrational uneasiness, but he put it down to habit. The past few days had formed it.

"We've been cartin' stuff for the soldiers," explained the driver as Lockley closed the door behind him. "They keep track of where that terror beam is workin', and they tell us by truck radio, and we dodge it. Ain't had a bit of trouble. Never thought I'd play games with Martians! Did you see any of 'em? What sort of critters are they?"

He slipped the truck into gear and gunned the motor. Truck and trailer, together, began to roll down the highway. Lockley was irritated with himself because he couldn't relax and feel safe, as this development seemed to warrant.

Later, he would wonder why he hadn't used his head in this as in other matters during the few days just past.

He plainly hadn't.