"It is open for you!" Hume broke the quiet first. His eyes were very bleak in his bony face.  
Vye stood up, took one step and was on the other side of the curtain where Hume's hand still found substance. He came back with the same lack of hindrance. Yes, to him there was no longer a barrier. But why—why him when Hume was still a prisoner?
 
The Hunter raised his head so his eyes could meet Vye's with the authority of an order. "Go, get away while you can!"
 
Instead Vye dropped down beside the other. "Why?" he asked baldly. And then the most obvious of all answers came.
 
He glanced at Hume. The Hunter's head lolled back against[75] the rock which supported him, his eyes were closed now, and he had the look of a man who had been driven to the edge of endurance and was now willing to relinquish his grip and let go.
 
Deliberately Vye brought up his right hand, balled his fingers into a fist. And just as deliberately he struck home, square on the point of that defenseless chin. Hume sagged, would have slipped down the surface of the rock had Vye's hands not caught in his armpits.
 
Since he had not the strength left to get to his feet with such a burden, Vye crawled, dragging the inert body of the Hunter with him. And this time, as he had hoped, there was no resistance at the gap. Unconscious, Hume was able to cross the barrier. Vye stretched him as comfortably flat as he could, used a portion of their water on his face until he moaned, muttered, and raised his hand feebly to his head.
 
Then those gray eyes opened, focussed on Vye.
 
"What—"
 
"We're both through now, both of us!" The younger man saw Hume glance around him with waking belief.
 
"But how—?"
 
"I knocked you out, that's how," Vye returned.
 
"Knocked me out? I crossed when I was unconscious!" Hume's voice steadied, strengthened. "Let me see!" He rolled over on his side, threw out his arm, and this time the hand found no wall. For him, too, the barrier was gone.
 
"Once through, you are free," he added wonderingly. "Maybe they never foresaw any escapes." He struggled up, sitting with his hands hanging loosely between his knees.
 
Vye turned his head, looked down the trail. The length of distance lying between them and the safari camp now faced them with a new problem. Neither of them could make that trek on foot.
 
"We're out, but we aren't back—yet," Hume echoed his thought.
 
"I was wondering, if this door is open—" Vye began.
 
"The flitter!" Again Hume's mind matched his. "Yes, if those globes aren't hanging around just waiting for us to try."
 
"They might act only to get us here, not to keep us once we're in." That might be wishful thinking, they wouldn't know until they tried to prove it.[76]
 
"Give me a hand." Hume held out his own, let Vye pull him to his feet. Weak as he was, he was clear-eyed, plainly clear-headed once more. "Let's go!"
 
Together they went back through the gap, then tested the absence of the barrier once more, to make sure. Hume laughed. "At least the front door remains open, even if we find the back one closed."
 
Vye left him sitting by that entrance while he made a quick trip to the cave to pick up the small pack of supplies left them. When he returned they crammed tablets into their mouths, drank feverishly of the lake water, and, with the stimulation of the new energy, set off along the cliff face.
 
"This wall in the lake," Hume asked suddenly, "you are sure it is artificial?"
 
"Runs too straight to be anything else, and those projections are evenly spaced. I don't see how it could be natural."
 
"We'll have to be sure."
 
Vye thought of that attacking water creature. "No diving in there," he protested. Hume smiled, a stretch of skin far too tight over his jaw now.
 
"Not us, at least not us now," he agreed. "But the Guild will send another survey."
 
"What could be the reason for all this?" Vye helped his companion over the loose debris of a cliff slide.
 
"Information."
 
"What?"
 
"Someone—or something—picked our brains while we were out of our heads. Or—" Hume paused suddenly, looked directly at Vye. "I have a vague feeling that you were able to keep going a lot better than I was. That so?"
 
"Some of the time," Vye admitted.
 
"That checks. Part of me knew what was going on, but was helpless while that other thing," his smile of moments earlier was wiped away, there was a chill edge in his voice, "picked over my brains, sorted out what it wanted."
 
Vye shook his head. "I didn't feel that way. Just thick-headed—as if I were sleep walking and yet awake."
 
"So it took me over, but didn't go all the way with you. Why? Another question for our list."
 
"Maybe—maybe Wass' techs fixed it so I couldn't be brain-picked, as you call it," Vye offered.[77]
 
Hume nodded. "Could be—would well be. Come on." He pressed the pace now.
 
Vye turned to look down the slope suspiciously. Had Hume another warning of menace out of the wood? He could sight no movement there. And from this distance the lake was a topaz sheet of calm which could hide anything. Hume was already several paces ahead, scrambling as if the valley monsters were again on their track.
 
"What's the matter?" Vye demanded, as he caught up.
 
"Night coming." Which was true. Then Hume added, "If we can reach the flitter before sunset, we'll have a chance to fly over the lake down there, to make a taping of it before we go."
 
The energy of the tablets strengthened them so that by the time they reached the crevice door they were moving with their former agility. For a single second Hume hesitated before that slit, almost as if he feared the test he must make. Then he stepped forward and this time into freedom.
 
They reached the ledge where the flitter perched just as they had seen it last. How long ago that had been they could not have told, but they suspected that days of haze hung in between. Vye searched the sky. No globes winking there—just the flyer alone.
 
He took his old seat behind the pilot, watched Hume test the relays and responses in the quick run down of a man who has done this chore many times before. But the other gave a little sigh of relief when he finished.
 
"She's all right, we can lift."
 
Again they both looked aloft, half fearing to see those malignant herders wink into being to forbid flight. But the sky was as serenely clear of even a drifting cloud as they could hope. Hume pressed a button and they arose vertically with an even progress totally unlike the leap which had taken them out of Wass' camp.
 
Well above the cliff wall they hovered, and were able to see below the round bowl of the valley prison. Hume touched controls, the flitter descended slowly just above the center of the lake. And from this position they were able to sight the other peculiarity of that body of water, that it was perfectly oval in shape, far too perfect to be an undeveloped product of nature. Hume took a round disk from his equipment belt, fitted it carefully into a slot on the control board[78] and pressed the button below. Then he sent the flitter in a weaving zigzag course well above the surface of the water, so that eventually the flyer passed over every foot of its surface.
 
And from above, in spite of the turgid quality of the liquid, they could see what did rest on the bottom of that oval. The wall with its sharp corner which Vye had noted from shore level was only part of a water covered erection. It made a design when seen from overhead, a six-pointed star surrounding an oval and in the midst of that oval a black blot which they could not identify.
 
Hume brought the flitter over in one last sweep. "That's it. We have a full taping."
 
"What do you think it is?"
 
"A ............