thousand-foot shell of the ZX-1 roared by it at equal altitude, making
it a puny fly-speck in the sky. But the fly-speck was faster. It
turned in a screaming bank; it straightened; it lunged back after the
swaying, retreating mammoth like a whippet, lower, now, than its
quarry. It maneuvered expertly as it gained, for one of the best
pilots of the service was at its controls, and there were deep lines
graven in his face, lines of anguish and intolerable suspense.

Through the telescopic sight, Chris had not seen a single white-clad
figure standing beside the glass ports of the dirigible's control car.
But he had seen, slung from the rack along her belly, a single
plane--the same rather peculiar-looking plane he had seen hanging
beneath the rack of the ZX-2 a few minutes before she had gone down in
flames!

And in that plane, he knew surely, was the answer to the mystery.

* * * * *

Speed cut to just a trifle more than the dirigible's. Chris passed a
few feet underneath the huge expanse of her lower directional rudder.
From so close, its uncontrolled wavering was terrifying.

His faculties were concentrated on the task of sliding the scout's
clamp into the groove of the plane rack, but he was also surveying the
lone airplane hanging from it. A powerful machine, painted in Navy
colors, a peculiar knob on the upper side of each half of the top wing
gave it its unfamiliar appearance. Its pilot was obviously aboard the
dirigible, working....

Closer and closer the scout crept, quarter-way now along from the
stern of the massive bulk that loomed above it, and within fifty feet
of the third clamp in the rack. Touchy work, maneuvering into it, with
the ZX-1 yawing as she was, and the need for haste desperate. Chris's
hands were glued to the stick: his nerves were as tight as violin
strings. Then, when only ten feet from the rack clamp, he gave a
startled jump of uncomprehending amazement.

The propeller of the mysterious plane ahead had roared over. Its clamp
had left the rack; it had dropped down in a perfectly controlled dive
and flattened out as if a master pilot were at its controls.

But the plane's cockpit was still empty, Chris could see; nor had he
seen any figure pass down the ladder from the dirigible into it!

Devoid of all emotion save bewilderment, he sat stupidly in the scout.
A moment later, so well had he aimed it, its clamp nestled snugly into
the groove of the rack,