"We believe that the Voornizar originate in some planetary system far beyond the awful void which surrounds our solar family. Long ago, they found their radium supply disappearing, and were forced to wander in search of new deposits. They developed the Ghlak-Ileth in their laboratories to do the work of removing the radium. They were probably planted as tiny eggs or spores, each with an infinitesimal bit of radium to furnish life energy. When the creatures hatched, their instinct was to dig downward. As they went, they fed on radium and other elements. "Thus, ever growing and multiplying, they remained, finally absorbing every bit of radium in the planet. After a fixed period, they became imbued with the impulse to return to the surface. There they were collected by the Voornizar, who returned at exactly the proper time, to extract the radium for their own use. The period of three thousand years is, we believe, the time necessary for a round trip from here to the habitat of the Voornizar. However, it may be only the period between meals--for time means nothing to them--nor do heat, cold or lack of atmosphere affect them." "How can we possibly combat such a menace?" asked Elene hopelessly. * * * * * "This time we Martians are ready," Klalmar-lan told them. "Before, we were forced to resort to pitiful devices such as lead lined boats, which shut out the deadly emanations of the _radon_ gas which seeped to the surface from the Ghlak-Ileth on the sea bottoms. But now we have developed a weapon--the choker ray, harmless to organisms like ourselves, but able instantly to halt any sort of disintegration, particularly radio-activity. It will stop the Voornizar instantly. "As soon as I recognized this Voornizar ship, I let her have the choker beam. She immediately lost headway, began to drift. I came alongside and boarded her, being careful to put on a space suit, for the Voornizar require no atmosphere, and would not be likely to have the ship's interior conditioned. I found what I expected. There was not a living creature, or moving piece of machinery aboard. I had heard the fearsome Ghosts described many times, but these were the first I had seen. Their silvery, amorphous bodies are said to glow with a blinding white effulgence, but in death, these had turned to a dull leaden hue. There were hundreds of them in the great ship, which seemed to me mostly occupied by machinery with which to attract and grapple the radium worms, and holds in which to store them. "On an upper deck, I found a row of small staterooms, which I thought wise to investigate. And well that I did, for my former presumption that nothing lived on the ship was not quite correct. That was one who _barely_ lived--" "Barely is the word, my friend," came a weak voice from the bunk, "I don't know what you did to those devils, but you sure stopped them in their tracks." Denny had recovered consciousness. The trio hurried to his side.