ng
through the air toward the Austrian airship.

It struck home and there was a terrible explosion, followed by several
sharp cries of pain, as the Austrian airship seemed to split into a
thousand pieces. A moment later these pieces disappeared.

The three friends turned upon Stubbs.

"What is this, magic?" asked Chester in surprise.

"No," replied Stubbs, quietly. "Melenite. I just happened to see a stick
of it here, so I threw it."

"Well, you did a pretty good job, Stubbs," said Colonel Anderson.

"I didn't pitch for my college team two years for nothing," returned
Stubbs modestly. "But now let's go down. I want to get my feet on the
ground again."

"It won't be much longer, Stubbs," said Hal. "Another two hours at this
speed should put us across the Serbian frontier. Just be patient."

"I'll wait," replied Stubbs, "but I won't promise to be patient."

He sank back to his place and refused to talk further.

While the big army craft is speeding across Austria it will be a
good time to explain the presence of the four friends in their
present predicament and introduce them briefly to those who have not
met them before.

Hal Paine and Chester Crawford were both American lads. With the former's
mother, they had been in Berlin at the outbreak of the great war, and,
after a series of interesting and exciting adventures, they made their
way to Liege just in time to take part in the defense of that stronghold
with the Belgian army.

There they won distinction and lieutenancies in the Belgian service, the
latter bestowed upon them by King Albert himself. They had been in France
with the British troops that had stopped the German drive on Paris and
had gone with the Allied army on its advance. They had seen service on
all fronts and now considered themselves veteran campaigners.

Colonel Anderson they had met in Berlin just after the Kaiser had
declared war upon France. The colonel, lieutenant then, and Major
Derevaux, a Frenchman, had taken the boys with them on their flight and
the four had later encountered each other in many strange and
unexpected places.

Stubbs they also had met while on one of their many missions and had
earned the little man's undying gratitude; but he had repaid whatever
they had done for him, with interest, more than once.

The boys, in their latest exploit, had been with the Italian army in
the Alps. Two of the four friends having fallen into the hands of the
enemy, the others had