When they returned to the cabin some time later, McAllen was in a pensive mood. He started a pot of coffee in the small kitchen, then quickly cleaned the tackle and put it away. Barney sat at the table, smoking and watching him, but made no attempt at conversation.

McAllen poured the coffee, produced sugar and powdered milk, and settled down opposite Barney. He said abruptly, "Have you had any suspicions about the reason for the secretive mumbo jumbo?"

"Yes," Barney said, "I\'ve had suspicions. But it wasn\'t until that happened"—he waved his hand at the wall out of which they appeared to have stepped—"that I came to a definite conclusion."

"Eh?" McAllen\'s eyes narrowed suddenly. "What was the conclusion?"

"That you\'ve invented something that\'s really a little too good."

"Too good?" said McAllen. "Hm-m-m. Go on."

"It doesn\'t take much power to operate the thing, does it?"

"Not," said McAllen dryly, "if you\'re talking about the kind of power one pays for."

"I am. Can the McAllen Tube be extended to any point on Earth?"

"I should think so."

"And you financed the building of this model yourself. Not very expensive. If the secret leaked out, I\'d never know who was going to materialize in my home at any time, would I? Or with what intentions."

"That," McAllen nodded, "is about the size of it."

Barney crushed out his cigarette, lit a fresh one, blew out a thin streamer of smoke. "Under the circumstances," he remarked, "it\'s unfortunate you can\'t get the thing shut off again, isn\'t it?"

McAllen was silent for some seconds. "So you\'ve guessed that, too," he said finally. "What mistake did I make?"

"None that I know of," Barney said. "But you\'re doing everything you can to keep the world from learning about the McAllen Tube. At the same time you\'ve kept it in operation—which made it just a question of time before somebody else noticed something was going on, as I did. Your plans for the thing appear to have gone wrong."

McAllen was nodding glumly. "They have," he said. "They have, Mr. Chard. Not irreparably wrong, but still—" He paused. "The first time I activated the apparatus," he said, "I directed it only at two points. Both of them within structures which were and are my property. It was fortunate I did so."

"T............