n that Stubbs' voice had carried to the occupants of
the second craft, and as Stubbs had exclaimed aloud in English there was
little doubt in the minds of our three friends that the Austrians would
seek an explanation. Nor were they wrong.

Came a hail from the Austrian:

"Who've you got aboard, there?"

"Prisoner," replied Hal, thinking quickly.

"What are you doing with him?"

"We--" Hal began, but the Austrian interrupted.

"Spies, that's what you are! Down to the ground now, or I'll put a hole
through you."

"Guess it's no use fooling any longer," muttered Hal.

He threw over the elevating lever and the large craft soared rapidly. At
the same moment a shot rang out from aboard the Austrian, followed by a
cry of surprise, and then the Austrian gave chase.

"Get your guns and see if you can pick 'em off," Hal instructed Chester
and Colonel Anderson. "I'll run this thing, but you fellows will have to
do the fighting."

"Suits me," responded Chester, examining his revolver carefully.

Colonel Anderson also nodded his agreement to this plan.

Hal now changed his course and the airship headed toward the south,
bearing off a trifle to the east, in a direction that he believed,
eventually, would land them in Serbia.

It became apparent now that the Austrian had not boasted of the speed of
his craft without reason, for he gained perceptibly.

"We can't out-run him, Hal," shouted Chester.

"Then we shall have to try something else," was the reply.

Abruptly he reduced the speed of the craft and the Austrians dashed in
range of the revolvers of the fugitives almost before they could have
realized it.

"Crack! Crack!"

Chester and Colonel Anderson had fired. There came a scream of pain from
behind and the Austrian craft wobbled crazily. A moment later a man
sprang to his feet, sought to retain his footing, threw up his arms and
went hurtling into space.

"Got one, Hal!" said Chester, quietly.

"Good!"

Came a volley of small arm fire from behind and bullets whined about the
four friends. Again Chester and Colonel Anderson fired almost
simultaneously and again their efforts were rewarded. A second man was
put out of the fight, as they could see.

At this moment Stubbs came into action.

He arose from his seat and, grasping the side of the speeding craft with
his left hand for support, stood to his full height. His right arm drew
back, then flashed sharply forward again and a small object went spinni