"A fair chance," he said. "We've got them spread nicely across the horns of a dilemma. If _they_ do grab me, it will prove that there's an enemy alien at work. If they don't grab me, I'll solve their secret--" [Illustration: As the crystal flashed, he vanished....] The crystal flashed pearly-white. Again it paralyzed the orthicon and crackled in the loudspeaker. It blinded Dave momentarily, but he shouted, "I'm still here!" He heard a cry from the far end of the sound system. It faded rapidly. * * * * * As his eyesight returned, Dave looked around curiously. The laboratory was still around him, but it had the same semi-ghostly appearance that Claverly and Phelps had had. Of the images of the two physicists Dave could see nothing. They had been there, faintly visible, when he had gone in. Now they were gone. Dave looked at the workbench. He passed a hand through it. He stamped on the floor and found that he was stamping _through_ the floor; he was actually standing on a semi-smooth surface a few inches below it. "Damn!" he swore. He looked around. The concrete walls of the building were heavy and thick; he could not see clearly through them. He walked forward, hands outstretched, and saw his hands enter the wall. He walked through the wall, and felt a slight resistance, as though he were walking through water. He burst through the far side and the released pressure pitched him headlong. Once outside, Dave looked around. In the ghostly distance he could see the main laboratory building and the jeep bearing Jane, DeLieb, and Howes. They came to the building and Dave ran to meet them. "I'm here," he called. He screamed it. He yelled at the top of his voice. Jane walked through him. Her face was broken, tears filled her eyes, and Dave tried desperately to get her attention. But she walked through him and went on. They went in the door; Dave walked back through the phantom wall and met them inside. "Dave!" cried Jane. She ran across the room and reached--then recoiled, her face twisted in horror. "Like Claverly, like Phelps," she whispered. "Like hell!" yelled Dave. "Dammitall, I'm here!" "Gone!" said Jane. "I'm not gone!" snapped Dave. But a still voice inside him said that he was. He looked carefully at the place Jane watched with horror-filled eyes. He could see nothing. Then he went to Jane and peered into her eyes. The pupils were clear. Dave snorted. If he could not see the image of himself that Jane saw, there was no reason why he could see a possible reflection of that image in her pupils. "So he proved it," said DeLieb. "And so we continue, knowing that something or someone is maliciously attacking us," said Howes. "It's mine," said Jane in a flat voice. "No--" said DeLieb. "I want to follow him," she said. "Don't be a fool!" yelled Dave.