"Why have they steered their twenty worlds across the outer void toward our galaxy? Where have they come from and for what?" Jhul Din asked. "We must learn the answer to these questions and report to headquarters. This matter may be of import to our whole galaxy." "Shall we descend and land on one of those dark stars to investigate, then?" asked Jhul Din. Quickly I considered. "There's no need to imperil our whole squadron," I said. I grasped the space-phone and spoke to the other ships. "It appears that these twenty dark stars are being deliberately propelled toward our galaxy, no doubt by beings of some sort upon them," I stated. "Our cruiser is going to descend to investigate. All others of the squadron will remain at their present level, and if we do not rejoin you within two hours you will return at full speed toward the galaxy and report what has happened at headquarters." From the captains of the other cruisers came assent to the order, and then I turned to the pilot. "Very well, Jan Allon--descend toward the foremost of the dark stars." * * * * * In tense silence Korus Kan and Jhul Din and I watched as our cruiser shot down through space toward the first of the onrushing dead suns. What would we find there? We waited in taut anticipation as the ship dropped down through the millions of miles. Presently Korus Kan spoke. "None of the dark stars seems to have any atmospheric halo," he said. "What kind of creatures could exist on worlds without atmosphere?" Jhul Din marvelled. The foremost dark-star's surface rushed up toward us. We saw on it crowded movement, a stir of hosts of moving things. "There's life of some kind down there, all right," said Jhul Din. Then as our ship raced lower an exclamation of utter astonishment came from me. "Life? This isn't a world of life as we know it. It's a world of machines!" For the moving things that existed in hosts on the dark star were all machines! The twilight surface of the star was crowded with their numbers. There were towering machines that stalked to and fro; many-limbed mechanisms such as I had never seen; and dozens of other kinds. The eye could not count them, so great were their numbers. There was no other life or moving things in sight. Here was mystery of the cosmos, dark, enigmatic. How came the active and apparently masterless machines to be peopling these dirigible worlds? "By the suns, there must be people of some kind here!" exclaimed Jhul Din. "If not, who made these machines?" Korus Kan uttered a sharp cry. "Dur Nal! Some of the machines are coming up toward us!" A hundred or more mechanisms had risen from the dark star and were flying swiftly up through space toward us. These mechanisms had no occupants, no operators. They were simply masterless machines flying in space, disk-like in shape and with tubes much like beam-tubes projecting from them. "They may be going to attack us," Jhul Din warned. "Shall we beam them?"