The madman turned, saw Jenks, and started to run. Jenks took after him. Up the staircase the madman rushed toward the roof. Teddy followed him two floors and then rushed out to take the elevators. The building in its mad swaying had made it impossible for the lifts to be operated. Teddy realized this with a distraught gulp in his throat. He returned to the stairway and took up the pursuit of the madman. The corridors were beginning to fill with screaming men and wailing girls. It was a sight never to be forgotten. Laboriously Jenks climbed story after story without getting sight of the madman. Finally he reached the roof. It was waving like swells on a lake before a breeze. He caught sight of the Mad Musician standing on the street wall, thirty stories from the street, a leer on his devilish visage. He jumped for him. The madman grasped him and lifted him up to the top of the wall as a cat might have lifted a mouse. Both men were breathing heavily as a result of their 15-story climb. The madman tried to throw Teddy Jenks to the street below. Teddy clung to him. The two battled desperately as the building swayed. The dense crowd in the street had caught sight of the two men fighting on the narrow coping, and the shout which rent the air reached the ears of Jenks. * * * * * The mind of the engineer was still working clearly, but a wild fear gripped his heart. His strength seemed to be leaving him. The madman pushed him back, bending his spine with brute strength. Teddy was forced to the narrow ledge that had given the two men footing. The fingers of the madman gripped his throat. He was dimly conscious that the swaying of the building was slowing down. His reason told him that Linane had found the wall socket and had stopped the sawing of the devil's bow on the engine of hell. He saw the madman draw a big knife. With his last remaining strength he reached out and grasped the wrist above the hand which held the weapon. In spite of all he could do he saw the madman inching the knife nearer and nearer his throat. Grim death was peering into the bulging eyes of Teddy Jenks, when his engineering knowledge came to his rescue. He remembered the top stories of the Acme building were constructed with a step of ten feet in from the street line, for every story of construction above the 24th floor. "If we fall," he reasoned, "we can only fall one story." Then he deliberately rolled his own body and the weight of the madman, who held him, over the edge of the coping. At the same time he twisted the madman's wrist so the point of the knife pointed to the madman's body. There was a dim consciousness of a painful impact. Teddy had fallen underneath, but the force of the two bodies coming together had thrust the knife deep into the entrails of the Mad Musician.