The struggle went on. The inventor, though past the prime of life, and worn down by excessive thought, had some strength left. Its duration was brief; but it was not to be despised while it lasted. He grasped the tall figure of Marcus Wilkeson by the neck with one arm, and with the other struck dozens of blows upon his face and chest. The comparative youth and freshness of Marcus were unable to free him from the strong hold of this vigorous old man. Pangs of terror shot through the heart of the poor girl as she saw that her father was about to become a murderer. Then the tide of fortune changed. Marcus, bruised and black in the face, and panting with exertion, released himself from the inventor's clutch, and, in turn, caught him by the throat. With his long arm he held the furious old man at a safe distance. The unhappy girl was now agonized with fears for her father's life. "This is madness. Let us stop it." Thus Pet heard Marcus Wilkeson say, in panting accents. What demoniac spell was it that prevented her from shrieking--"Stop it. In God's name, father, stop?" "Never!" said the undaunted old man. "Never, till I have thrown you headlong down stairs! Liar! Villain!" With that, Pet saw her father hurl himself, with the ferocity of a tiger, on Marcus Wilkeson. Such was the suddenness and impetuosity of the movement, that Marcus was pushed back several feet toward the door, from the centre of the room, where the most obstinate part of the struggle had taken place. But the old man's supremacy was short lived. The younger and stronger man suddenly stooped, caught the inventor with both hands under the arms, and thrust him toward the corner occupied by the mysterious machine. The inventor would have fallen on it, and perhaps have been instantly killed by contact with some portion of the brass or iron work, but for the interposition of the screen. This broke his fall. He scrambled to his feet, full of rage, and foaming at the mouth. Marcus stepped back, and said, "Now let it cease." Pet saw her father snatch something that looked like a club, from some part of the machine. "This is my answer," he said, and precipitated himself with fresh fury upon Marcus. The younger man had expected the attack, and braced himself for it. He caught the inventor by the arm that held the club, or other weapon. They wrestled for its possession--the inventor with frenzy in every feature, Marcus with fixed determination, and silently. The weapon was now aloft--now below--now shifted in the twinkling of an eye to the right, and now to the left. At one time the inventor seemed to be on the point of securing it; at another, Marcus. Suddenly Pet saw it whirl like a shillelah above her father's head, with a strange noise like the quick winding of a clock. Then she heard a dull sound, as of striking a board with a brick, and--she saw her father fall to the floor. At the same moment, the light in the room went out, and all was darkness.