re was brownish earth with small green
patches and beyond was sere brown range. At seventeen thousand feet
there were simply no details.

Soon the clouds were merely a white-tipped elevation of the white haze
to the sides and behind. And then there came a new sound above the
droning roar of the motors. Joe heard it--and then he saw.

Something had flashed down from nowhere. It flashed on ahead and banked
steeply. It was a fighter jet, and for an instant Joe saw the distant
range seem to ripple and dance in its exhaust blast. It circled
watchfully.

The transport pilot manipulated something. There was a change in the
sound of the motors. Joe followed the co-pilot's eyes. The jet fighter
was coming up astern, dive brakes extended to reduce its speed. It
overhauled the transport very slowly. And then the transport's pilot
touched one of the separate prop-controls gently, and again, and again.
Joe, looking at the jet, saw it through the whirling blades. There was
an extraordinary stroboscopic effect. One of the two starboard
propellers, seen through the other, abruptly took on a look which was
not that of mistiness at all, but of writhing, gyrating solidity. The
peculiar appearance vanished, and came again, and vanished and appeared
yet again before it disappeared completely.

The jet shot on ahead. Its dive brakes retracted. It made a graceful,
wallowing, shallow dive, and then climbed almost vertically. It went out
of sight.

"Visual check," said the co-pilot drily, to Joe. "We had a signal to
give. Individual to this plane. We didn't tell it to you. You couldn't
duplicate it."

Joe worked it out painfully. The visual effect of one propeller seen
through another--that was identification. It was not a type of signaling
an unauthorized or uninformed passenger would expect.

"Also," said the co-pilot, "we have a television camera in the
instrument board yonder. We've turned it on now. The interior of the
cabin is being watched from the ground. No more tricks like the phony
colonel and the atom bomb that didn't 'explode.'"

Joe sat quite still. He noticed that the plane was slanting gradually
downward. His eyes went to the dial that showed descent at somewhere
between two and three hundred feet a minute. That was for his benefit.
The cabin was pressurized, though it did not attempt to simulate
sea-level pressure. It was a good deal better than the outside air,
however, and yet too quick a descent meant discomfort. T