Let's
go!"

On the board before him the tiny neon tube flickered dully, glowed
briefly like a piece of red-hot iron, then went out. In a moment it was
glowing again, and then quickly its brilliance mounted till it was a
line of crimson. Morey snapped the switch from the general radar to the
beam receiver, that he might locate the machine exactly. It was fully a
minute before the neon tube flashed into life once more. The pirate was
flying just ahead of the big plane, very likely gassing them. All
around him were the Air Guardsmen, unaware that the enemy was so near.
As the disrupter beam could be projected only about a mile, they would
have to dive down on the enemy at once; an instant later the great plane
beneath them seemed to be rushing upward at a terrific speed.

The two radar beams were kept focused constantly on the Pirate's craft.
When they were about two miles from the two planes, the neon tube blazed
brilliantly with a clash of opposing energy. The Pirate was trying to
maintain his invisibility, while the rapidly growing strength of the
machine above strove to batter it down. In moments the ammeter connected
with the disrupter beam began to rise so rapidly that Morey watched it
with some concern. Despite the ten-kilowatt set being used to project
the beam, the resistance of the apparatus on board the pirate ship was
amazing.

Abruptly the three became aware of a rapidly solidifying cloud before
them. The interference of the beam Morey was sending had begun breaking
down the molecular oscillation that permitted the light to pass freely
through the pirate's craft. Suddenly there was a circle of blue light
about the shadow form, and a moment later the ionized air relapsed into
normal condition as the pirate's apparatus broke down under the strain.
At once Morey shut off his apparatus, convinced by the sudden change
that the pirate's apparatus had blown out. He glanced up quickly as
Arcot called to him, "Morey--look at him go!"

Too late. Already the plane had shot off with terrific speed. It had
flashed up and to their left, at a rate of climb that seemed
unbelievable--except that the long trail of flaming gas told the story!
The plane was propelled by rockets! The terrific acceleration carried it
out of their range of vision in an instant, and as Arcot swung the ship
to bring him again within sight of the windows, they gasped, for already
he was many miles away.

There was a terrific wrench as Arcot threw