a very different matter. I want you to learn all you possibly
can so as to be prepared for anything."

Jimbo felt vaguely uncomfortable when she talked like this.

"But you'll be with me in the Escape Flight--the final one of all," he
said; "and nothing ever goes wrong when you're with me."

"I should like to be always with you," she answered tenderly, "but it's
well to be prepared for anything, just the same."

And more than this the boy could never get out of her.

On one of these lonely flights, however, he made the unpleasant
discovery that he was being followed.

At first he only imagined there was somebody after him because of the
curious vibrations of the very rarefied air in which he flew. Every time
his flight slackened and the noise of his own wings grew less, there
reached him from some other corner of the sky a sound like the
vibrations of large wings beating the air. It seemed behind, and
generally below him, but the swishing of his own feathers made it
difficult to hear with distinctness, or to be certain of the direction.

Evidently it was a long way off; but now and again, when he took a spurt
and then sailed silently for several minutes on outstretched wings, the
beating of distant, following feathers seemed unmistakably clear, and he
raced on again at full speed more than terrified. Other times, however,
when he tried to listen, there was no trace of this other flyer, and
then his fear would disappear, and he would persuade himself that it had
been imagination. So much on these flights he knew to be
imagination--the sentences, voices, and laughter, for instance, that
filled the air and sounded so real, yet were actually caused by the wind
rushing past his ears, the rhythm of the wing-beats, and the tips of the
feathers occasionally rubbing against the sides of his body.

But at last one night the suspicion that he was followed became a
certainty.

He was flying far up in the sky, passing over some big city, when the
sound rose to his ears, and he paused, sailing on stretched wings, to
listen. Looking down into the immense space below, he saw, plainly
outlined against the luminous patch above the city, the form of a large
flying creature moving by with rapid strokes. The pulsations of its
great wings made the air tremble so that he both heard and felt them. It
may have been that the vapours of the city distorted the thing, just as
the earth's atmosphere magnifies the rising or setting of the m