Racing toward the south another flier sped toward Helium. In its cabin a tall red man bent over the soft sole of an upturned sandal. With delicate instruments he measured the faint imprint of a small object which appeared there. Upon a pad beside him was the outline of a key, and here he noted the results of his measurements. A smile played upon his lips as he completed his task and turned to one who waited at the opposite side of the table. “The man is a genius,” he remarked. “Only a genius could have evolved such a lock as this is designed to spring. Here, take the sketch, Larok, and give all thine own genius full and unfettered freedom in reproducing it in metal.” The warrior-artificer bowed. “Man builds naught,” he said, “that man may not destroy.” Then he left the cabin with the sketch. As dawn broke upon the lofty towers which mark the twin cities of Helium—the scarlet tower of one and the yellow tower of its sister—a flier floated lazily out of the north. Upon its bow was emblazoned the signia of a lesser noble of a far city of the empire of Helium. Its leisurely approach and the evident confidence with which it moved across the city aroused no suspicion in the minds of the sleepy guard. Their round of duty nearly done, they had little thought beyond the coming of those who were to relieve them. Peace reigned throughout Helium. Stagnant, emasculating peace. Helium had no enemies. There was naught to fear. Without haste the nearest air patrol swung sluggishly about and approached the stranger. At easy speaking distance the officer upon her deck hailed the incoming craft. The cheery “Kaor!” and the plausible explanation that the owner had come from distant parts for a few days of pleasure in gay Helium sufficed. The air-patrol boat sheered off, passing again upon its way. The stranger continued toward a public landing stage, where she dropped into the ways and came to rest. At about the same time a warrior entered her cabin. “It is done, Vas Kor,” he said, handing a small metal key to the tall noble who had just risen from his sleeping silks and furs. “Good!” exclaimed the latter. “You must have worked upon it all during the night, Larok.” The warrior nodded. “Now fetch me the Heliumetic metal you wrought some days since,” commanded Vas Kor. This done, the warrior assisted his master to replace the handsome jewelled metal of his harness with the plainer ornaments of an ordinary fighting man of Helium, and with the insignia of the same house that appeared upon the bow of the flier. Vas Kor breakfasted on board. Then he emerged upon the aerial dock, entered an elevator, and was borne quickly to the street below, where he was soon engulfed by the early morning throng of workers hastening to their daily duties.