On the heights of the lower canyon entrance, Grenfell's second camp was being established. There was no way for Dorrek's men and brues to get out of the valley without passing through one of these two narrow gorges, both of which Grenfell's projectors now dominated.

Across the dark rocky distance, in the direction of the Light Country, Jimmy thought he could distinguish the tiny lights of the other camp six miles away. Overhead a small group of girls winged off in that direction.

"Look!" exclaimed Roc suddenly.

They turned. Behind them, in the darkness a mile back on this upper plateau, was turmoil. Vague blurred sounds in the heavy, motionless night air. Tiny flashes of blue-green lightlittle beams leaping down, crossing with others leaping up. It lasted only a moment or two. The beams were extinguished; the sounds died. Jimmy learned afterward that a small group of armed girls, flying to investigate the surrounding country, had come upon a few of Dorrek's lurking men. And a brue. The men and the brue were killed, and three of the girls.

Grenfell now established patrols for all this neighborhood.

At intervals they passed overhead, flying low with their searchbeams sweeping the crags.

It was a painfully long hobble for Jimmy, but at last he and Roc came to the brink of the cliff. In the center of the valley Dorrek had set up a ring of giant projectors, a mile in diameter, within which his army was enclosed. They were pointed directly upward, spreading beams of blue-green. At a few hundred feet above the ground they crossed, mingled into a solid curtain of light, a circular, mile-wide upstanding funnel.

It was queerly non-radiant, this barrage; inherently bluegreen, but it did not illumine the valley. The rocky floor, even close to where the projectors were set, was solid black. Nor did it radiate much heat. Within the beams of that thin, glowing curtain, the temperature must have been several thousand degrees centigradeforty times the boiling point of water perhaps. But twenty feet away, its heat could scarcely be felt.

The effective height of this heat barrage was two miles, or less. The Cube could sail over it, drop a bomb, blow the Mercurian ball to bits.

Jimmy's thoughts raced. At the base of the barrage curtain, where the spreading beams came from the projectors, there were triangular holes of unprotected darkness. Five hundred feet on the rocks, narrowing to the point where the beams met overhead. Into those triangular holes Grenfell could creepup to the silver ball. A vague glow of light seemed to disclose the round silver shape of the ball lying in the center of the encampment.

Jimmy had conceived that Dorrek's barrage was immovable.

The holes in it so easy to penetrate) But within a minute he saw that was not so. One of the projectors swung suddenly forward. Its beam swept the empty valley floor, almost reached the base of the cliff, darted sidewise, then upward and back to its former position. It made Jimmy shudder.

Nothing living could have withstood the briefest touch of that faint lurid glow.

GrenfelTs projector at the canyon mouth presently sent down an answering beam. Its source was along the clifftop not far from where Rooand Jimmy were crouching. Its range was something near a mile; it swept the nearby valley floor, dominated the exit, but could not reach Dorrek's projectors.

After a moment it was extinguished.

"The storm is coming," said Roc.

"A black storm?"

"Yes." The clouds overhead ' were shot with occasional turgid yellow shafts. They illumined the valley far more than did the enemy barrage beams. The air here on the cliffs was cold.

A little wind had sprung up fitfully.

"We had better go back," Roc added. "The storm may burst now, or in an hour or two."

"Soon, Roc." Presently, as an experiment, Grenfell tried a shot from the long-range Earth gun on the deck of the Cube. But Dorrek's men were alert. The gun spat yellow; instantly one of the barrage projectors bent downward. The shell went into the beam, exploded harmlessly in mid-flight over the valley.

"I'm going down there," Jimmy said suddenly. "Roc, you've got to help me. Get our platformassemble our gills. We're going down." In the darkness he could not see Rocs face.

"Yes. I will try."

"Now listen-" A sudden thought struck Jimmy. "If you see Guy and Toh, tell them what we're doing. Maybe they'd like to come" If only Jimmy had insisted on that! Roc was on his feet. In the darkness Jimmy could only hear his voice. "Very well. You wait here. If I see Tama, I will ask her to come. Down there in the darkness, if trouble should arise, we could send Tama quickly up for help." As Jimmy hesitated. Roc added vehemently: "I am not one who would want Tama placed in danger. But just to land in the darkness down therenot too dangerous."

"O.K. Hurry it." Jimmy sat alone on the clifftop through another interval, staring down at the distant enemy barrage. The projectors could not sweep the ground since their long range would annihilate the projector next in line, he noticed.

Suddenly he saw a hand heat-beam dart sidewise from near one of the projectors. It swept the ground with a range of nearly a hundred feet. And a guard at the neighboring projector answered it with a similar horizontal beam.

Jimmy smiled grimly. That was not so good. But his fabric suit might withstand that smaller beam. He would have to chance it.

His attention was distracted by the beat of wings close over his head. Roc arriving with their platform? But it was not. Another platform, seven girls on each of its sides, went sailing past. Fifty feet over Jimmy, and twice that far beyond the brink of the clifFtop: Two men were crouching on the platform.

A sudden silent burst of yellow-red radiance in the sky briefly illumined themGuy and Toh I They did not see Jimmy. He stood up impulsively, cursed his leg, and hastily sat down again.

The platform winged away, but Jimmy did not lose sight of it, as it headed off toward Grenfells other camp. But it rose steeply and presently came back. Then in a broad spiral, almost directly over Jimmy's head, it mounted.

Grenfell was making another test. The platform was a mere dot against the turgid sky. Great funnel-shaped clouds were slowly wheeling up there. Queer green and yellow shafts occasionally burst in them.

The platform rose steadily. A mile? Two miles? Twelve or fifteen thousand feet? Then Jimmy realized: Guy and Toh were trying to fly acioss the top of the barrage curtain to test the height and try to drop a bomb.

The little dot up there began moving out over the valley.

Dorrek's men had seen it. There was a movement of all of the barrage beams. They turned diagonally inward, closing at the top almost together in a mingled blurred glow.

The platform crossed over them. The falling bomb was Invisible to Jimmy at first. But then he saw it strike the upper reaches of the barrage funnel as a glowing point of light.

Its metal shell turning luminous. The heat was weak at first. But in a second or two the falling dot of fire burst into a puff of flame. A tiny report echoed over the silent valley.

The platform came sailing back, descending well behind Jimmy, lost in the darkness of the upper plateau.

A rush of wings sounded behind Jimmy. His platform, complete with its crew of fourteen girls, landed near the brink.

Jimmy saw Roc and Tama dismounting. They came toward him.

Tama greeted him: "Jimmy, you must not try this thing.

Roc has told me" He waved away her protests.

"Don't worry, TamaI'm no cripple. I'm sparing myself nowyou wait until you see how I can make speed when I have to. You going with us, TamaP"

"Yes," said Roc quietly. "For a little way." They mounted the platform. Jimmy saw three knives, three small hand cylinders and a flashlight in the weapon rack.