"No need to quarrel," Tempelmar drawled pleasantly, "though our visitor's suggestions do sound rather peculiar to minds tempered to a realistic materialism. Nevertheless, it is our duty to safeguard the world from any real dangers, no matter how improbable or remote. So, considering the evidence, we must not pass lightly over our visitor's theory that alien minds are usurping those of Earth--at least not until there has been an opportunity to advance alternate theories." "Alternate theories _have_ been advanced, tested, and discarded," said Clawly sharply. "Of course," Tempelmar agreed smilingly. "But in science that's a process that never quite ends, isn't it?" He sat down, Conjerly following suit as if drawn. Clawly was irascibly conscious of having got the worst of the interchange--and the lanky, sleepy-eyed Tempelmar's quiet skepticism had been more damaging than Conjerly's blunt opposition, though both had told. He felt, emanating from the two of them, a weight of personal hostility that bothered and oppressed him. For a moment they seemed like utter strangers. He was conscious of standing too much alone. In every face he could suddenly see skepticism. Shielding was the worst--his expression had become that of a man who suddenly sees through the tricks of a sleight-of-hand artist masquerading as a true magician. And Thorn, who should have been mentally at his side, lending him support, was sunk in some strange reverie. He realized that even in his own mind there was a growing doubt of the things he was saying. Then, utterly unexpectedly, adding immeasurably to his dismay, Thorn got up, and without even a muttered excuse to the men beside him, left the room. He moved a little stiffly, like a sleepwalker. Several glanced after him curiously. Conjerly nodded. Tempelmar smiled. Clawly noted it. He rallied himself. He said, "Well, gentlemen?" III. But who will reveal to our waking ken The forms that swim and the shapes that creep Under the waters of sleep? _The Marshes of Glynn_, Sidney Lanier. Like a dreamer who falls head-foremost for giddy miles and then is wafted to a stop as gently as a leaf, Thorn plunged down the main vertical levitator of the Opal Cross and swam out of it at ground level, before its descent into the half mile of basements. At this hour the great gravity-less tube was relatively empty, except for the ceaseless silent plunge and ascent of the graduated subtronic currents and the air they swept along. There were a few other down-and-up swimmers--distant leaflike swirls of color afloat in the contracting white perspective of the tube--but, like a dreamer, Thorn did not seem to take note of them.