the single toggle below it. A scene grew, showing a white-haired
army colonel seated behind a desk, facing them.

"Ken--it's Dr. Halsey," Carol whispered.

"_Was_ Dr. Halsey," said Ken heavily. "I used to wonder if we had the
same instructors."

The officer's lips moved. "Hello, Ken and Carol. I've been selected to
make this film to greet you, and I know both of you will return to see
it." His eyebrows lifted in the quizzical expression they knew well.
"I'm going to rattle off a lot of explanations and suggestions, but I
imagine the first thing you'll want to know is how all the things you've
seen could have happened so quickly. And knowing that, will clarify the
rest.

"You remember the experiments the Air Force made, sending small animals
above the stratosphere. By means of controlled diets and more
complicated devices you'll find explained in a book, we learned that
these animals were not subjectively experiencing the time-span they
should have aloft. In effect, they were aging hardly at all away from
gravity--the farther away, the less aging.

"We got some fairly accurate figures on the time-distance ratios.
Briefly, assuming you held to your course until you were recalled, you
can figure that an average of ten years has elapsed on the earth's
surface for every hour you were in space."

Ken muttered, "We were actually out of atmosphere about twenty-four
hours. That would make it the year--"

"About 2200," finished Carol breathlessly.

"... how or why, but that Time was evidently a variable. The realm of
physics was a madhouse--discreetly so, lest our enemies profit by our
knowledge. There is no visual or other subjective means to sense the
deceiving change in time-rate, or its illogical effects; we knew, for
instance, that you would not see the moon as a solid ring girding a
gyroscopic earth, as might seemingly be expected.

"Your message of recall was a record, slowed down to be within an
intelligible range of fast chatter or slow drawl when you received it.
We could have told you to open the envelope at a certain time or
distance, but even minutes and miles were critical and"--the pictured
features smiled paternally--"we knew your interest in each other might
cause a delay, while"--the expression changed to serious sympathy--"we
didn't know just when Space-Fear would strike."

Carol blushed and laid her cheek against Ken's chest. "They knew
everything that would happen, didn't they? They--they _planned