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."

"that was this cabin and the place on mallorca?"

"yes. the main operational sections of the tube are concealed about my california home. but certain controls have to be installed at any exit point to make it possible to return. it wouldn't be easy to keep those hidden in any public place.

"it wasn't until i compared the actual performance of the tube with my theoretical calculations that i discovered there was an unforeseen factor involved. to make it short, i could not—to use your phrasing—shut the tube off again. but that would certainly involve some extremely disastrous phenomena at three different points of our globe."

"explosions?" barney asked.

"weee-ll," mcallen said judiciously, "implosions might come a little closer to describing the effect. the exact term isn't contained in our vocabulary, and i'd prefer it not to show up there, at least in my lifetime. but you see my dilemma, don't you? if i asked for help, i revealed the existence of the tube. once its existence was known, the research that produced it could be duplicated. as you concluded, it isn't really too difficult a device to construct. and even with the present problem solved, the mcallen tube is just a little too dangerous a thing to be at large in our world today."

"you feel the problem can be solved?"

"oh, yes." mcallen took off his glasses and rubbed his eyes. "that part of it's only a matter of time. at first i thought i'd have everything worked out within three or four years. unfortunately i badly underestimated the expense of some of the required experimentation. that's what's delayed everything."

"i see. i had been wondering," barney admitted, "why a man with something like this on his mind would be putting in quite so much time fishing."

mcallen grinned. "enforced idleness. it's been very irritating really, mr. chard. i've been obliged to proceed in the most inexpensive manner possible, and that meant—very slowly."

barney said, "if it weren't for that question of funds, how long would it take to wind up the operation?"

"a year—perhaps two years." mcallen shrugged. "it's difficult to be too exact, but it certainly wouldn't be longer than two."

"and what would be the financial tab?"

mcallen hesitated. "a million is the bottom figure, i'm afraid. it should run closer to a million and a half."

"doctor," barney said, "let me make you a proposition."