--"

"No," Barney said. "I guarantee that you'll have all the time you want
for your own problem." He smiled. "Considering what you told me, I'd
like to hear that one's been solved myself!"

McAllen grinned briefly. "I can imagine. Very well. Ah ... when can
you let me have the money, Mr. Chard?"

* * * * *

The sun was setting beyond the little lake as Barney drew the shades
over the cabin window again. Dr. McAllen was half inside the built-in
closet at the moment, fitting a pair of toggle switches to the
concealed return device in there.

"Here we go," he said suddenly.

Three feet from the wall of the room the shadowy suggestion of another
wall, and of an open door, became visible.

Barney said dubiously, "We came out of _that_?"

McAllen looked at him, sad, "The appearance is different on the exit
side. But the Tube's open now--Here, I'll show you."

He went up to the apparition of a door, abruptly seemed to melt into
it. Barney held his breath, and followed. Again there was no sensory
reaction to passing through the Tube. As his foot came down on
something solid in the shadowiness into which he stepped, the living
room in Sweetwater Beach sprang into sudden existence about him.

"Seems a little odd from that end, the first time through, doesn't
it?" McAllen remarked.

Barney let out his breath.

"If I'd been the one who invented the Tube," he said honestly, "I'd
never have had the nerve to try it."

McAllen grinned. "Tell you the truth, I did need a drink or two the
first time. But it's dead-safe if you know just what you're doing."

Which was not, Barney felt, too reassuring. He looked back. The door
through which they had come was the one by which they had left. But
beyond it now lay a section of the entrance hall of the Sweetwater
Beach house.

"Don't let that fool you," said McAllen, following his gaze. "If you
tried to go out into the hall at the moment, you'd find yourself right
back in the cabin. Light rays passing through the Tube can be shunted
off and on." He went over to the door, closed and locked it, dropping
the key in his pocket. "I keep it locked. I don't often have visitors,
but if I had one while the door was open it could be embarrassing."

"What about the other end?" Barney asked. "The door appeared in the
cabin when you turned those switches. What happens now? Suppose
someone breaks into the cabin and starts prowling around--is the door
still