"We can fly directly in," Loto added. "It's the entrance to the subterranean chambers where the scientists work--and where they store their apparatus under guard. It's also a museum, where relics of the past are gathered." George relapsed into an awed silence, staring down at the city. In the streets and on the housetops, people were standing, gazing up at the plane curiously. The mouth of the cavern grew steadily larger as the plane swooped down upon it. The yawning hole seemed to have a level floor extending horizontally back into the mountain. Far back into the darkness, little blue lights twinkled. "You'd better take the controls, Loto," Rogers said anxiously. "I don't like the idea of flying into that." Loto slipped quietly into the seat. The Frazia motors stopped abruptly. Silently, with only the sound of the air rushing past, the plane glided swiftly downward. Around the cavern mouth was a small platform with a roof over it, built on an overhanging ledge of rock. The figures of three men seated there were visible. Abruptly one of the men rose, and from his upflung hand a tiny flash of blue-white light shot into the clouds overhead. Even in the daylight it was a plainly visible flash. "Lightning!" George exclaimed and, as though to confirm him, a little miniature crack of thunder sounded an instant later. "They know I'm coming," Loto said. It was a queer sensation, darting into that blackness. The cave mouth seemed to open and swallow them. The plane struck the ground with a bump, lifted, bumped again and rolled forward. Points of light swept past on either side; a blue-white glare lay ahead. The plane slackened its speed and came to a stop. "We're here," said Loto. "Take only what you will need at once. We can come back here later today or tomorrow." Quickly, they descended from the plane. The hum of dynamos sounded from far away in the mountain's depths. The roof high overhead was dimly visible, and great shadows, flickering blue-white lights, were everywhere. Near at hand, where the cave broadened, was a space more brightly lighted. Further along it narrowed again, forming a dozen branching passages. An incline fifty feet wide sloped down into blackness, with a faint pencil-point of blue light shining from far down within its recesses. "Why, the whole mountain is honeycombed!" Rogers exclaimed. "Yes, sir. Just stand here a minute and I'll be with you. Don't move about!" Figures were approaching, robed in black rubber garments, gloved and hooded. Loto turned to greet them, and they drew back their hoods, disclosing their heads and faces. There was a brief conversation, then Loto turned back to his companions. "Fahn is at home in the city," he said swiftly, and his tone was concerned. "We'll go there." The black-robed figures gazed at them curiously a moment; then went back to their work. Led by Loto, the three started off toward the mouth of the cave. "Is your plane in here, Loto?" Rogers asked.