"The evidence," said Lockley as Jill looked at him ashen-faced, "the evidence is all for monsters. But there was something in that broadcast that calls for courage, and I want to summon it. We're going to need it."

"If they aren't monsters," said Jill in a stricken voice, "Then—then they're men. And we have a cold war with only one country, and they're the only ones who'd play a deadly trick like this. So if they aren't monsters, in the ship, they must be men, and they'd kill anybody who found it out."

"But again," insisted Lockley, "the evidence is still all for monsters. You've been very loyal and very confident about Vale. But we're in a fix. Vale would want you in a safe place, and there's something in that broadcast that doesn't look good."

"What was in the broadcast?"

Lockley said wryly, "Two things. One was there and one wasn't. There wasn't anything about soldiers marching up to Boulder Lake to welcome visitors from wherever they come from, and to say politely to them that as visitors they are our guests and we'd rather they didn't shoot terror beams or paralysis beams about the landscape. We were more or less counting on that, you and I. We were expecting soldiers to come up the highway headed for the lake. But they aren't coming."

Jill, still pale, wrinkled her forehead in thought.

"That's what wasn't in the broadcast," Lockley told her. "This is what was. The troops have formed a cordon about the Park. They've run into the terror beam. The broadcast said it was weakened by distance and only made the soldiers uncomfortable. But they've moved back. You see the point? They've moved back!"

Jill stared, suddenly understanding.

"But that means—"

"It means," said Lockley, "that the terror beam is pretty much of a weapon. It has a range up in the miles or tens of miles. We don't know how to handle it yet. Whoever or whatever arrived in the thing Vale saw, it or they has or have a weapon our Army can't buck, yet. The point is that we can't wait to be rescued. We've got to get out of here on our own feet. Literally. So we forget about highways. From here on we sneak to safety as best we can. And we've got to put our whole minds on it."

Jill shook her head as if to drive certain thoughts out of it. Then she said, "I guess you're right. He would want me to be safe. And if I can't do anything to help him, at least I can not make him worry. All right! What does sneaking to safety mean?"

Lockley led her down the highway running from Boulder Lake to the outside world. They came to a blasted-out cut for the highway to run through. The road's concrete surface extended to the solid rock on either side. There was no bare earth to take or hold footprints, and there was a climbable slope.

"We go up here and take to the woods," said Lockley, "because we're not as easy to spot in woodland as we'd be on a road. The characters at the lake will know what roads are. If we figure out how to handle their terror beam, they'll expect the attack to come by road. So they'll set up a system to watch the roads. They ought to do it as soon as possible. So we'll avoid notice by not using the roads. It's lucky you've got good walking shoes on. That could be the deciding factor in our staying alive."

He led the way, helping her climb. There would be no sign that they'd abandoned the highway. In fact, there'd be no sign of their existence except the small smashed car. Lockley's existence was known, but not his and Jill's together.

Lockley did not feel comfortable about having deliberately shocked Jill into paying some attention to her own situation instead of staying absorbed in the possible or probable fate of Vale. But for them to get clear was going to call for more than sentimentality on Jill's part. Lockley couldn't carry the load alone.

There was an invasion in process. It could be, apparently, an invasion from space, in which case the terror produced would be terror of the unknown. But Lockley had conceived of the possibility that it might be an invasion only from the other side of the world. Such an invasion was thought of by every American at least once every twenty-four hours. The fears it would arouse would be fears of the all too thoroughly known.

The whole earth had the jitters because of the apparently inevitable trial of strength between its two most gigantic powers. Their rivalry seemed irreconcilable. Most of humanity dreaded their conflict with appalled resignation because there seemed no way to avoid it. Yet it was admittedly possible that an all-out war between them might end with all the world dead, even plants and microbes in the deepest seas. It was ironic that the most reasonable hope that anybody could have was that one or the other nation would come upon some weapon so new and irresistible that it could demand and receive the surrender of the other without atomic war.

Atom bombs could have done the trick, had only one nation owned them. But both were now armed so that by treacherous attack either could almost wipe out the other. There was no way to guard against desperate and terrible retaliation by survivors of the first attacked country. It was the certainty of retaliation which kept the actual war a cold one—a war of provocation and trickery and counter-espionage, but not of mutual extermination.

But Lockley had suggested—because it was the worst of possibilities—that America's rival had developed a new weapon which could win so long as it was not attributed to its user. If the United States believed itself attacked from space, it would not launch missiles against men. It would ask help, and help would be given even by its rival if the invasion were from another planet. Men would always combine against not-men. But if this were a ship from no farther than the other side of the earth, and only pretended to be from an alien world ... America could be conquered because it believed it was fighting monsters instead of other men.

This was not likely, but it was believable. There was no proof, but in the nature of things proof would be avoided. And if his idea should happen to be true, the disaster could be enormously worse than an invasion from another star. This first landing could be only a test to make sure that the new weapon was unknown to America and could not be countered by Americans. The crew of this ship would expect to be successful or be killed. In a way, if an atom bomb had to be used to destroy them, they would have succeeded. Because other ships could land in American cities where they could not be bombed without killing millions; where they could demand surrender under pain of death. And get it.

Lockley looked at the sun. He glanced at his watch.

"That would be south," he indicated. "It's the shortest way for us to get to where you'll be reasonably safe and I can tell what I know to someone who may use it."

Jill followed obediently. They disappeared into the woods. They could not be seen from the highway. They could not even be detected from aloft. When they had gone a mile, Jill made her one and final protest.

"But it can't be that they aren't monsters! They must be!"

"Whatever they are," said Lockley, "I don't want them to lay hands on you."

They went on. Once, from the edge of a thicket of trees, they saw the highway below them and to their left. It was empty. It curved out of sight, swinging to the left again. They moved uphill and down. Now the going was easy, through woods with very little underbrush and a carpet of fallen leaves. Again it was a sunlit slope with prickly bushes to be avoided. And yet again it was boulder-strewn terrain that might be nearly level but much more often was a hillside.

Lockley suddenly stopped short. He felt himself go white. He grasped Jill's hand and whirled. He practically dragged her back to the patch of woods they'd just left.

"What's the matter?" The sight of his face made her whisper.

He motioned to her for silence. He'd smelled something. It was faint but utterly revolting. It was the smell of jungle and of foulness. There was the musky reek of reptiles in it. It was a collection of all the smells that could be imagined. It was horrible. It was infinitely worse than the smell of skunk.

Silence. Stillness. Birds sang in the distance. But nothing happened. Absolutely nothing. After a long time Lockley said suddenly, "I've got an idea. It fits into that broadcast. I have to take a chance to find out. If anything happens to me, don't try to help me!"

He'd smelled the foul odor at least fifteen minutes before, and had dragged Jill back, and there had been no other sign of monsters or not-monsters upon the earth. Now he crouched down and crawled among the bushes. He came to the place where he'd smelled the ghastly smell before. He smelled it again. He drew back. It became fainter, though it remained disgusting. He moved forward, stopped, moved back. He went sideways, very, very carefully, extending his hand before him.

He stopped abruptly. He came back, his face angry.

"We were lucky we couldn't use the car," he said when he was near Jill again. "We'd have been killed or worse."

She waited, her eyes frightened.

"The thing that paralyzes men and animals," he told her, "is a projected beam of some sort. We almost ran into it. It's probably akin to radar. I thought they'd put watchers on the highways. They did better. They project this beam. When it blocks a highway, anybody who comes along that highway runs into it. His eyes become blinded by fantastic colored lights, and he hears unbearable noises and feels anguish and they smell what we smelled just now. And he's paralyzed. Such a beam was turned on me yesterday and I was captured. A beam like that on the highway at the lake paralyzed three men who were carried away, and later two others whose car ditched and who stayed paralyzed until the beam was turned off."

"But we only smelled something horrible!" protested Jill.

"You did. I rushed you away. I'd smelled it before. But I went back. And I smelled it, and I crawled forward a little way and I began to see flashes of light and to hear noises and my skin tingled. I pushed my hand ahead of me—and it became paralyzed. Until I pulled it back." Then he said, "Come on."

"What will we do?"

"We change our line of march. If we drove into it or walked into it we'd be paralyzed. It's a tight beam, but there's just a little scatter. Just a little. You might say it leaks at its edges. We'll try to follow alongside until it thins out to nothing or we get where we want to go. Unless," he added, "they've got another beam that crosses it. Then we'll be trapped."

He led the way onward.

They covered four miles of very bad going before Jill showed signs of distress and Lockley halted beside a small, rushing stream. He saw fish in the clear water and tried to improvise a way to catch them. He failed. He said gloomily, "It wouldn't do to catch fish here anyhow. A fire to cook them would show smoke by day and might be seen at night. And whatever's at the Lake might send a terror beam. We'll leave here when you're rested."

He examined the stream. He went up and down its bank. He disappeared around a curve of the stream. Jill waited, at first uneasily, then anxiously.

He came back with his hands full of bracken shoots, their ends tightly curled and their root ends fading almost to white.

"I'm afraid," he observed, "that this is our supper. It'll taste a lot like raw asparagus, which tastes a lot like raw peanuts, and a one-dish meal of it won't stick to your ribs. That's the trouble with eating wild stuff. It's mostly on the order of spinach."

"I'll carry them," said Jill.

She actually looked at him for the first time. Until she found herself anxious because he was out of sight for a long time, she hadn't really regarded him as an individual. He'd been only a person who was helping her because Vale wasn't available. Now she assured herself that Vale would be very grateful to him for aiding her. "I'm rested now," she added.

He nodded and led the way once more. He watched the sun for direction. Two or three miles from their first halt he said abruptly, "I think the terror beam should be over yonder." He waved an arm. "I've got an idea about it. I'll see."

"Be careful!" said Jill uneasily.

He nodded and swung away, moving with a peculiar tentativeness. She knew that he was testing for the smell which was the first symptom of approach to the alien weapon.

He halted half a mile from where Jill watched, resting again while she gazed after him. He moved backward and forward. He marked a place with a stone. He came well back from it and seemed to remove his wrist watch. He laid it on a boulder and stamped on it. He stamped again and again, shifting it between stampings. Then he pounded it with a small rock. He stood up and came back, trailing something which glittered golden for an instant.

He halted before he reached the rock he'd placed as a marker. He did cryptic things, facing away from Jill. From time to time there was a golden glitter in the air near him.

He came back. As he came, he wound something into a little coil. It was the silicon bronze mainspring of his non-magnetic watch. He held it for her to see and put it in his pocket.

"I know what the terror beam is—for what good it'll do!" he said bitterly. "It's a beam of radiation on the order of radar, and for that matter X-rays and everything else. Only an aerial does pick it up and this watchspring makes a good one. I could barely detect the smell at a certain place, but when I touched the laid out spring, it picked up more than my body did and it became horrible! Then I moved in to where my skin began to tingle and I saw lights and heard noises. The spring made all the difference in the world. I even found the direction of the beam."

Jill looked frightened.

"It comes from Boulder Lake," he told her. "It's the terror beam, all right! You can walk into it without knowing it. And I suspect that if it were strong enough it would be a death ray, too!"

Jill seemed to flinch a little.

"They're not using it at killing strength," said Lockley coldly. "They're softening us up. Letting us find out we're frustrated and helpless, and then letting us think it over. I'll bet they intended the four of us to escape from that compost pit thing so we could tell about it! But we'll know, now, if we find dead men in rows in a wiped-out town, we'll know what killed them, and when they ask us politely to become their slaves, we'll know we'll have to do it or die!"

Jill waited. When he seemed to have finished, she said, "If they're monsters, do you think they want to enslave us?"

He hesitated, and then said with a grimace, "I've a habit, Jill, of looking forward to the future and expecting unpleasant things to happen. Maybe it's so I'll be pleasantly surprised when they don't."

"Suppose," said Jill, "that they aren't monsters. What then?"

"Then," said Lockley, "it's a cold war device, to find out if the other side in the cold war can take us over without our suspecting they're the ones doing it. Naturally those in this ship will blow themselves up rather than be found out."

"Which," said Jill steadily, "doesn't offer much hope for...."

She didn't say Vale's name. She couldn't. Lockley grimaced again.

"It's not certain, Jill. The evidence is on the side of the monsters. But in either case the thing for us to do is get to the Army with what I've found out. I've had a stationary beam to test, however crudely. The cordon must have been pushed back by a moving or an intermittent beam. It wouldn't be easy to experiment with one of those. Come on."

She stood up. She followed when he went on. They climbed steep hillsides and went down into winding valleys. The sun began to sink in the west. The going was rough. For Lockley, accustomed to wilderness travel, it was fatiguing. For Jill it was much worse.

They came to a sere, bare hillside on which neither trees nor brushwood grew. It amounted to a natural clearing, acres in extent. Lockley swept his eyes around. There were many thick-foliaged small trees attempting to advance into the clear space. He grunted in satisfaction.

"Sit down and rest," he commanded. "I'll send a message."

He broke off branches from dark green conifers. He went out into the clearing and began to lay them out in a pattern. He came back and broke off more, and still more. Very slowly, because the lines had to be large and thick, the letters S.O.S. appeared in dark green on the clayey open space. The letters were thirty feet high, and the lines were five feet wide. They should show distinctly from the air.

"I think," said Lockley with satisfaction, "that we might get something out of this! If it's sighted, a 'copter might risk coming in after us." He looked at her appraisingly. "I think you'd enjoy a good meal."

"I want to say something," said Jill carefully. "I think you've been trying to cheer me up, after saying something to arouse me—which I needed. If the creatures aren't monsters, they'll never actually let anybody loose who's seen that they aren't. Isn't that true? And if it is—"

"We know of six men who were captured," insisted Lockley, "and I was one of them. All six escaped. Vale may have escaped. They're not good at keeping prisoners. We don't know and can't know unless it's mentioned on a news broadcast that he's out and away. So there's absolutely no reason to assume that Vale is dead."

"But if he saw them, when he was fighting them—"

"The evidence," insisted Lockley again, "is that he saw monsters. The only reason to doubt it is that they blindfolded four of us."

Jill seemed to think very hard. Presently she said resolutely, "I'm going to keep on hoping anyhow!"

"Good girl!" said Lockley.

They waited. He was impatient, both with fate and with himself. He felt that he'd made Jill face reality when—if this S.O.S. signal brought help—it wasn't necessary. And there was enough of grimness in the present situation to make it cruelty.

After a very long time they heard a faint droning in the air. There might have been others when they were trudging over bad terrain, and they might not have noticed because they were not listening for such sounds. There were planes aloft all around the lake area. They'd been sent up originally in response to a radar warning of something coming in from space. Now they flew in vast circles around the landing place of that reported object. They flew high, so high that only contrails would have pointed them out. But atmospheric conditions today were such that contrails did not form. The planes were invisible from the ground.

But the pilots could see. When one patrol group was relieved by another, it carried high-magnification photographs of all the park, to be developed and examined with magnifying glasses for any signs of activity by the crew of the object from space.

A second lieutenant spotted the S.O.S. within half an hour of the films' return. There was an immediate and intense conference. The lengths of shadows were measured. The size and slope and probable condition of the clearing's surface were estimated.

A very light plane, intended for artillery-spotting, took off from the nearest airfield to Boulder Lake.

And Lockley and Jill heard it long before it came in sight. It flew low, threading its way among valleys and past mountain-flanks to avoid being spotted against the sky. The two beside the clearing heard it first as a faint mutter. The sound increased, diminished, then increased again.

It shot over a minor mountain-flank and surveyed the bare space with the huge letters on it. Lockley and Jill raced out into view, waving frantically. The plane circled and circled, estimating the landing conditions. It swung away to arrive at a satisfactory approach path.

It wavered. It made a half-wingover, and it side-slipped crazily, and came up and stalled and flipped on its back and dived....

And it came out of its insane antics barely twenty feet above the ground. It raced away as close as possible to touching its wheels to earth. It went away behind the mountains. The sound of its going dwindled and dwindled and was gone. It appeared to have escaped from a deliberately set trap.

Lockley stared after it. Then he went white.

"Idiot!" he cried fiercely. "Come on! Run!"

He seized Jill's hand. They fled together. Evidently, something had played upon the pilot of the light plane. He'd been deafened and blinded and all his senses were a shrieking tumult while his muscles knotted and his hands froze on the controls of his ship. He hadn't flown out of the beam that made him helpless. He'd fallen out of it. And then he raced for the horizon. He got away. And it would appear to those to whom he reported that he'd arrived too late at the distress-signal. If fugitives had made it, they'd been overtaken and captured by the creatures of Boulder Lake, and there'd been an ambush set up for the plane. It was a reasonable decision.

But it puzzled the pilot's superior officers that he hadn't been allowed to land the plane before the beam was turned on him. He could have been paralyzed while on the ground, and he and his plane could have yielded considerable information to creatures from another world. It was puzzling.

Lockley and Jill raced for the woodland at the clearing's edge. Lockley clamped his lips tight shut to waste no breath in speech. The arrival and the circling of the plane had been a public notice that there were fugitives here. If the beam could paralyze a pilot in mid-air, it could be aimed at fugitives on the ground.... There could be no faintest hope....

Wholly desperate, Lockley helped Jill down a hillside and into a valley leading still farther down.

He smelled jungle, and muskiness, and decay, and flowers, and every conceivable discordant odor. Flashes of insane colorings formed themselves in his eyes. He heard the chaotic uproar which meant that his auditory nerves, like the nerves in his eyes and nostrils and skin, were stimulated to violent activity, reporting every kind of message they could possibly report all at once.

He groaned. He tried to find a hiding-place for Jill so that if or when the invaders searched for her, they would not find her. But he expected his muscles to knot in spasm and cramp before he could accomplish anything.

They didn't. The smell lessened gradually. The meaningless flashings of preposterous color grew faint. The horrible uproar his auditory nerves reported, ceased. He and Jill had been at the mercy of the unseen operator of the terror beam. Perhaps the beam had grazed them, by accident. Or it could have been weakened....

It was very puzzling.