"I'm going out ... alone," he said firmly to Palanth and Lucero. "I owe the inhabitants of this world a debt, and whether we remain or not, is for them to decide. You see this star-like jewel? That's the Star of Panadur; by concentrating my thoughts, it acts as a sort of transmitting crystal and will make it possible for me to reach the leader of the Panadurs. I will return." He smiled reassuringly into Lucero's distraught face, and Palanth's scowling one. "Why can't I accompany you?" The Martian growled. "Since when must I be left behind in the face of danger? Am I an old woman, Mark?" "But there's no danger, Palanth! It's a promise I gave that never, never would I bring any intelligent creature to Panadur without their approval. This world's a treasure house, and the Panadurs are a treasure in themselves, for their fur is finer than anything in the Universe, including Neptune's moons. I know of a vast cavern floored with oxide, and cliffs of pure metal. Europa, or rather, Panadur, is an inexhaustible source of power! It remains with them--the Panadurs, whether we remain or not." He smiled at them again, almost pleadingly, for them to understand, and without another word, stepped through the air-locks and was gone. They could see his tall figure in its gleaming sheath outlined in the unearthly glow until it disappeared in the distance. * * * * * Mark Lynn let his mind be passive. Contact with the alien intelligence had been made; the jewel in his hand was now a burst of radiance, as he traversed the valley in the direction of the cavern country, and at last he was before the gigantic mass of cliffs he sought. He entered a low, gallery-like cave that wound downwards into the bowels of the cliff, following the twisting turns as the gallery widened and the luminescent walls became even more luminous, until at the end of a turn a burst of radiance met his eyes and he was once more in the grotto of titanic proportions lighted by the glaucous radiance, like the green light beneath the waters of a shallow sea. At his feet, crystalline and powdery, the entire floor of the grotto was covered by oxide as far as his eyes could see. Mark had the odd sensation of living a part of his life over again. He waited in silence. Mark knew that thousands of burning beryl eyes were peering at him from concealed openings in the walls; he felt the mental rapport with their leader that was rapidly absorbing from his mind all that could be obtained. The wait was interminable. At last, a silvery-grey, furred being, was before Mark, seemingly having come from nowhere. Its exquisite triangular face, with the wide-set beryl eyes and broad forehead, was startlingly human.