“What of it?” she flared. “You do things fully as complex every time you blast a vortex. . . . Oh, that’s it! Treat it as though it were a problem in n-dimensional differential equations, but don’t let your subconscious do it alone—get right down there and work with it—do that and you’ll have it all!” She seized his hands, squeezed them hard, and spoke aloud, the better to drive home the intensity of her convictions. “Buckle down, Storm, and dig . . . you can do it, I know you can do it. I _know_ you can . . . dig in, big fellow . . . you don’t have to pay _too_ much attention to detail; get a chain started, like a zipper, and it’ll finish itself . . . dig, Storm, DIG!” Storm dug. His jaw-muscles tightened into lumps. Sweat beaded his face and trickled down his chest under his shirt. And suddenly something happened. Not very much of anything, but something. Something more than mere contact, but not a penetration—more like a fusion—a fusion which, however instead of spreading rapidly to completion, as Joan had said it would, existed for the merest perceptible instant of time in an almost infinitesimal area and then vanished as instantaneously as it had come. But there was no doubt whatever that he had read, for an instant, a tiny portion of Joan’s mind; there was no chance whatever that she had sent him _that_ thought—in fact, she had been thinking at herself, not at him. And as he perceived the tenor of that thought he let go all his mental holds; tried frantically to bury the stolen thought so deeply that Joan would never, _never_ find out what it had been. . . . No, not bury it, either. Flesh, rock, metal—any material substance was perfectly transparent to thought. What wasn’t? A thought-screen. He didn’t have one, of course, but he knew the formula, and if he thought about that formula hard enough it might create interference enough. The catch would be whether he could talk at the same time . . . he probably could, if the subject matter didn’t require concentration. Joan, of course, knew instantly when Cloud pulled his mind away from hers; and, not waiting to ask why in words, drove in a probe to find out. Much to her surprise, however, her beam of mental force was stopped cold; she could not touch Cloud’s mind at all! “A block!” she exclaimed unbelievingly. “A real dilly, too—as hard and tight as a D7M29Z screen! What did you do, anyway, Storm, and how? I didn’t feel you get in!” He did not reply immediately. He was too busy; for, besides holding the screen-thought, he was also analyzing and studying the thought he had stolen from Joan: separating it out and arranging it into meaningful English words. It was amazing, how many words could be contained in one flashing, fleeting burst of thought.