They surveyed each other appraisingly. Eddie was mystified by the happenings of the day and was curious to learn more concerning these mythical invisible creations. It was inconceivable that the scientist had spoken truly of his accomplishment. Yet, he had done some marvelous things with Universal and, maybe--well, anyway, there was the girl. "Come with me," Shelton was saying: "I believe you're a square shooter, Vail." He was leading the way along the gravel path at the side of the house. Before them loomed the squat brick building that was the laboratory. The door crashed open before Shelton's hand had reached the knob, and one of those buzzing, unseen, monstrosities rushed clanking by, knocking the scientist from his feet in its passage. Ponderous, speeding footsteps crunched the gravel of the path, and then, with a wild thrashing of the underbrush alongside, the thing was gone. Eddie bent over the prostrate man and saw that he was unconscious. A thin trickle of blood ran from a cut in the side of his head. "Lina! Lina!" called Eddie frantically. For the first time in his life he was genuinely frightened. * * * * * He half carried, half dragged the limp body through the door of the laboratory and propped it in a chair. It required but a moment for him to see that Shelton's injury was inconsequential. He had only been stunned and already showed signs of recovering. "What is it, Mr. Vail? What's happened?" came the voice of Lina Shelton breathlessly. She was framed in the doorway, dressed now and panting from her exertions in responding to his call. "Oh, it's father," she wailed, dropping to her knees at his side. "He's been hurt. Badly, too." "No, not badly, Miss Shelton. He'll be around in a minute. I'm sorry to have excited you, but when I called I feared it was worse than it is." He was washing the blood from her father's small wound as he spoke. She took the basin from his hand, spilling some of the water in her eagerness. "Here, let me have that cloth," she demanded. Eddie admired her as her deft fingers took up the task. She was as exquisite in a simple sport outfit as she had been in her bathing suit. The scientist opened his eyes after a moment. Remembrance came at once and he sat erect in the chair, staring. "Lina!" he exclaimed, grasping her hand conclusively. "You're here, thank God! I dreamed--oh, it was horrible--I dreamed they had you." He clung to her closely. "They?" she murmured inquiringly. "Yes. Two of them are loose now. It's danger for you, my dear. You must leave at once. No, no--I can't let you out of my sight until they are captured or destroyed." He rose to his feet in his agitation and shook his head to clear it. He looked pleadingly at Eddie as if expecting him to offer a solution of the difficulty.