* * * * * Endlessly the road stretched before them. But the end came unexpectedly. So exhausted were the four that they scarcely realized that the silvery radiance of the tunnel had given place to a reddish glow, brighter and reminiscent of volcanic activity. Desquer lifted his hand in warning. He went on to reconnoitre, and presently beckoned the others. His burly figure was rigid, Tony saw. And, as he went on, he saw something else. The tunnel ended. It opened upon a cavern. A cavern that was a world! A world beneath a desert and a sea! Alu, the Land of Light, lay before the adventurers, and human eyes had never gazed upon a stranger sight. A metropolis of antiquity, with the wrecks of mighty buildings and fallen pillars strewing the flat floor of the cave. It was like Pompeii, and far older than Pompeii. It was grander than Karnak, more alien than crumbling Ang-kor-Vat. In the distance a pyramid rose toward the roof of the cave—touching it, supporting it as the fabled tree Yggdrasil is supposed to support the Earth. Red light flamed from beyond the pyramid. Alu! Old beyond imagination, cradle of a race that had ruled long and long ago! Alu, which the Egyptians had incorporated into their mythology as their heaven. The sheer, overwhelming majesty of the panorama struck the men dumb, as a hand might strike an impious lip. Huge and desolate and dead the lost world stretched before them, holding its secret fast, as it had held it since before the Pharaohs reigned. No wonder the pyramids were a mystery—built by some alien science. The same science that had reared the colossal structures of Alu! A hundred feet away a square white marble building towered, Doric pillars on either side of its open gateway. Some indefinable urge drew Tony’s eyes to it. Desquer said, “Hear that?” The others listened, but detected no sound. The commander grunted. “It came from that temple. Get your guns ready. We’re going in. If there’s trouble, shoot first.” The four moved softly across the flat rock of the floor. Halfway to the door of the building Jimmy clutched Tony’s arm. He pointed, his face chalk-white. “Look at that!” Tony followed his brother’s gaze, as did the others. Far away were two structures connected by an arched span. Across this span figures were moving. Figures with human bodies—but inhuman heads! At the distance it was impossible to make out details, but it was plain that there was something definitely abnormal about the beings who walked across the span. They moved in stately file and were gone. Jimmy whispered: “Remember what the priest said? The gods live in Alu!” Tony thought of the Egyptian gods, men with the heads of beasts and birds and reptiles. Could some monstrous hybrids have survived in this cavern? He shrugged off the thought. “Masks, Jimmy! Don’t be an idiot. Come on.”