He let the vent remain open but a few seconds, knowing that Sert's army, scattered and ready now, in a thousand secret nooks throughout the domed city-state, would see the signal, know that the dome turret was in friendly hands, and attack the Masters. And he was right. Even as the _impervite_ section slid back into its accustomed position he heard the Underling siren sound from one distant corridor--then another sounded, and another, and another, until from every weaving tunnel of the labyrinth that was this future city Larry heard the ear-splitting tumult that was madness and death to the Masters. Then a small company of Underlings burst from one tunnel. Larry leaped from the turret, grasped the leader, thrust him into the control room and shouted, "Guard this! I have a little job to take care of!" Jaw set, eyes hard, he was off toward the laboratory where--if the gods were good to him--he would find the girl he loved and the miserable parody of a man whom he most certainly did not love. As he ran, his footsteps followed the tempo of an ever-increasing volume of sound. Never before, he thought, since the creation of the world had begun in the high celestial music of the spheres, had mankind ever fought a life-and-death battle with such an accompaniment. All about him--it seemed from every corridor, out of each vibrant metal wall, through every air duct that fed the gigantic new world labyrinth--came the hideous howling of the electrosonic intensifiers which had been his invention. His trip was not a short one, and as he sped toward the laboratory he saw many men, both friends and antagonists. The Underlings, straight-shouldered with a confidence born of the up-reaching hope for liberty, were moving ever onward and onward against the foes. Armed with lances, crude swords, whatever tools and instruments they could lay hands on, they were pouring from the recesses of the city-state to charge upon the heart of the city, where dwelt the Masters. And in the van of each group was one Underling who carried as his weapon a small, square box in which a whirling disc made music of madness. Larry saw no pitched battles. This was a strange warfare; one in which the Masters possessed superior armaments--but could not use them. Time and again a lone Master would break from some cubicle to face, for a moment, the advancing host of erstwhile slaves. For seconds his heat-ray gun would pour scorching death into their fore, blasting into blackened hulks those who led. But ever and again the Master, snapping on his golden force-field as protection against the meaner weapons of the Underlings, would fall prey to the ear-bursting delirium of the howler; would stagger, would scream and reach for his _menaudo_, would die in a mist of shrieking madness. And then, suddenly, Larry was near his goal, and from a side corridor a familiar figure was racing toward him. It was Sert, and the Underling chieftain's face was radiant with joy.