Potter turned his nose downward, swooping like a preying eagle, and as he volplaned he swerved. He was flying on a level with Cantor's machine, approaching it from the rear. Hildegarde saw the blue shape of a revolver in Potter's hand and bent forward, tense, breathless for the event. Cantor, unconscious that he did not occupy the heavens alone, sped onward with singleness of purpose. He was unaware of danger, unconscious of near-flying menace. Potter did not want it so. He could not attack a man, an unconscious man, from behind. What he wanted was combat, man to man conflict. Even a spy bent on treacherous mission of destruction he could not destroy without warning. Swiftly his 'plane drew alongside Cantor's machine, passed it, and as it passed Potter looked at his adversary, saw his wide eyes fixed upon him with unbelieving astonishment. Then Cantor was left behind. Potter mounted, turned, approached again. Flashes of fire spat out from Cantor's machine, bullets droned harmlessly by.... It was as Potter wished it. He did not fire himself. He was not ready yet, but passed Cantor, circled again and came up from the rear. He was capable, he knew, of circling Cantor's machine. For every mile Cantor could traverse Potter traversed two. Now he drew to a position at the side of Cantor's 'plane again, wing-tip almost touching wing-tip. He could see Cantor's face distorted by rage and apprehension; saw Cantor lift his arm, saw the spurt of fire from his revolver. The bullet plowed through Potter's coat behind his shoulders.... Almost simultaneously he answered the fire with his automatic, once, twice, thrice.... He turned in his seat as he passed, but Cantor was still erect, his machine still under control. Again he repeated the maneuver. Again Cantor fired at point-blank range--and missed. Once more Potter's automatic spluttered.... Cantor lurched forward, his machine veered, seemed to wabble in the air--and Potter sped away, mounting, circling. As he returned he saw Cantor's machine careening crazily; saw it dip, plunge, tip perilously with no intelligence to hold it in control.... Then, suddenly, it pointed its nose downward and plunged.... Potter held his breath. He found himself counting, "One--two--three--four--five--six--" Not like an arrow, not like a plummet, but like a weighted leaf, the aeroplane fell.... Potter leaned far over to watch. Hildegarde, awed in the face of this happening, peered over also, fascinated.... The 'plane seemed to merge with the earth--with the ice of the lake. Then there was a mighty burst of flame, a gigantic, cataclysmic sound which dwarfed the roar of the motor; which seemed to tear the very air into shreds and to threaten to rock the moon in its distant sky.... Potter's machine rocked and dipped as the blast of air surged upward.... It righted itself and moved onward, smoothly, peacefully--the sole occupant of the sky.