w one
catch fire and begin its earthward swoop. Then the fuselage crackled
beside him, and his instrument board dissolved into ruin.
Instinctively he went round in a tight bank and loosed his
machine-gun. Nothing there! Nothing at all! Yet his right wing went
ragged, and his own furious blasts into the sky, their echoes drowned
by the roar of his propeller, were productive of nothing.

* * * * *

He shot past the uninjured plane, signalling it to descend. He wasn't
going to let his men ride aloft to helpless butchery. Nothing could be
done until some means was discovered of counteracting the enemy's
terrific advantage.

He darted across the heart of the city to where another of the flight
was circling, waggling his wings to indicate to it to descend. Then on
to the next plane and the next, shepherding them. Thank God they
understood! They were bunching toward the hangar. Yet another took
fire and dropped, a burning wreck. Half his flight out of commission,
and not an enemy visible!

He was aloft alone now, courting death--instant, invisible death. He
wouldn't descend until that carnival of murder was at an end. But it
was not at an end. Another crash, far up Pennsylvania Avenue, showed
an attempt upon the Capitol. Again--again, and a smoking hell wreathed
the noble buildings so that it was no longer possible to see them. A
lull, and then a crash nearer the city's heart. Crash! Crash!

Invisible though the enemy was, it was easy to trace the movements of
this particular plane by the successive areas of destruction that it
left behind it. It was coming back over Pennsylvania Avenue, dropping
its bombs at intervals. It was methodically wiping out an entire
section of Washington.

Dick drove his plane toward it. There was one chance in a thousand
that, if he could accurately gauge the progress of his invisible
antagonist, he could crash him and go down with him to death. If he
could get close enough to feel his prop-wash! A wild chance, but
Dick's mind was keyed up to desperation. He shot like an arrow toward
the scene, with a view to intercepting the murderer.

Then of a sudden he became aware of a curious phenomenon. A black beam
was shooting across the sky. A black searchlight! It came from the
flat top of a large hotel that had somehow escaped the universal
destruction, and, with its gaunt skeleton of structural steel showing
in squares, towered out of the ruin all about it like a