Nathan said nothing, but dropped to the floor. He adjusted the rifle to automatic fire, and lay in the opening of the niche. He pressed the trigger and a river of fire swept across the floor and flowed about the base of the boulder that hid Tabor--and under it! The boulder rested on narrow, jagged faces, between which there were openings. It was through these that Tabor had been firing and Nathan had glimpsed the secret of his protection. The flame raced about Tabor in a torrent of light. It leaped upon him and outlined him as if in St. Elmo's fire. He jerked up in searing pain, and in that instant a single shot came from across the cavern and found its mark. The fire died before Tabor fell, but the sound of his dead body smashing to the floor was loud in the dark silence. "Your father's murder is avenged," said a voice from across the cavern. "Firebird. I thought--" "I had to make you think what I made Tabor think. I threw a stone to give him a target. There was no protection out here. I had only one shot to risk." Nathan rushed towards the sound of her voice, and crushed her close to him to reassure himself that she was unharmed. In the light of the Jewels that was now pouring from the niche he could almost see her face. It seemed rich with gladness. The light was flickering now like auroral curtains of fire. "What is it?" murmured Nathan. "Wait--you'll see. This is what I've lived for. My work is finished now." It seemed to Nathan that they stood there for an interminable length of time while the light rose and fell, but gradually swelled until they could see each other plainly. There came a high note like the far away tinkling of chimes. The Jewels were rising from the floor. Firebird's hand on his arm restrained Nathan from rushing forward. "Wait," she commanded. The Jewels rose higher and then they began to float out of the niche towards the two Earthlings, carrying their ghostly light with them. [Illustration: _The Jewels rose higher, carrying their ghostly light with them._] Nathan stared. Where there had been only six Jewels in the niche, there were now seven floating in the air. Three were end to end, forming a vertical pillar. Around this pillar the other four formed a rotating square. As it rotated faster or slower the pitch of the musical note rose or fell. The singing, floating Jewels came nearer ... vibrating with the forces of life. And then out of the midst of them a voice spoke. "You have done well. You have my gratitude. I shall reward you." Nathan felt a prickling of the back of his neck. And suddenly Firebird clutched his arm and was sobbing faintly. "Are we too late?" she asked. "The ship of Plar has waited long, but the Envoys are patient. They await my report." The Jewels wheeled in the air and sped towards the tunnel ramp that bore upward to the surface. "Come," the voice said. Mechanically, Firebird followed. Nathan moved beside her, not looking back at the fallen Tabor.