A series of similar words followed, and as the experiment took this new direction David's nervousness vanished. Then, without warning, the travel series was taken up again; and this time each word came like the blow of a hammer upon a nail that is swiftly and surely driven to its mark. There was no mistaking the result. David's limbs stiffened, as if to ward off a blow. His look of relief gave place to a hopeless sort of misery; the telltale electric finger jumped forward in exaggerated lines as if to escape from some merciless pursuer. "South America," demanded Leighton. "Spaniards," after a pause, was David's answering word. "Mountains." "Muleback." "Lake." "Gold." The answers were hesitatingly given, almost inaudible. Again Una protested. "Stop!" she commanded. "You have no right----" Leighton waved her imperiously aside. "Dynamite," he continued, addressing David. "Darkness," came the hesitating answer. "Raoul Arthur." Silence. A weird dance, as of some mocking spirit, seized the electric finger pointing at the mirror. Una knelt at David's side, her hands upon his shoulders. His lips quivered as he looked despairingly at her. "Guatavita," said Leighton harshly. No answer. The electrodes slipped from David's grasp. The finger of light became suddenly motionless. David had fallen, unconscious, in Una's arms. V THE SEARCH FOR EL DORADO "Leave him with me," said Leighton. "Wait for us with Mrs. Quayle." "No! No!" answered the girl passionately, kneeling beside David, who was lying on the couch. "You have killed him!" "Don't talk nonsense," he said coldly, yet with sympathy in his keen gray eyes. "This had to be, and I took my own way about it. Now, go. He is all right. He is safe with me." David drew a long breath. He looked vacantly at Leighton, then turned to Una. "Do as he says," he whispered. "David, I will stay with you." "Not now; I must speak to your uncle." "David!" She looked into his eyes, trying to read there the mystery that was parting them. "It will be better for all of us," said Leighton gruffly. Unable to hide her fears, Una rose and moved away from them. The boards of the well worn floor creaked harshly as she walked to the far end of the room. Pausing at the door, she looked back. "I will wait for you," she said. When the sound of her footsteps died away, David turned to the old man, who was busied with his scientific apparatus. "Well, how do you feel?" asked Leighton, gathering up the notes which were strewn on the little table. "Curiously here," replied David, drawing his hand across his forehead. Then he asked: "How did you know?"