Old Kelvin Martin strained futilely against the rope that held immovable his thin wrists. A crimsoned bruise raced across his forehead where Vance had slugged him with a heavy hand. "Don't be a complete fool, Vance!" he said harshly. "That machine can't bring you anything but trouble!" The scientist's burly assistant glanced wearily up from where he coupled heavy batteries in series at the rear of the glittering machine that entirely filled one corner of the windowless room. "Shut up," he said t