undivided attention to the other craft, which by this time had drawn close to them.

"Man wig-wagging forward, Hal," said Chester.

"I see him," replied Hal, "but I can't make out his signals. Can you,
Anderson?"

"No, I can't. He evidently has something to say, though."

"Well," said Hal, "we'll have to hold a sudden council of war. What are we going to do about it? Shall we stop and talk, trying to fool him, or shall we run for it?"

"Well, if we were going to run, it would have been better before he got so close," said Chester. "Guess we may as well see what he has to say. These Austrian uniforms won't come in bad. You do the talking, Hal."

Hal nodded.

"All right," he said.

He reduced the speed of the machine and the Austrian came closer.

"Ahoy, there!" he said in German. "Who are you?"

"Lieutenant Drizladaz, attached to the Austrian army at Trieste," Hal shouted back.

"What are you doing here?"

"Mission," Hal yelled.

"Where to?"

Hal thought quickly.

"Greece," he said finally.

"What for?"

"That," said Hal, "is none of your business. I have my orders and I haven't time to fool around here with you. I'm due back to-morrow night."

There was a moment's silence from the other machine and then a voice called:

"Has your mission anything to do with Greece's intervention in the war?"

"Well, I can't say anything about that," replied the lad, thinking to give the other the impression that it was.

"I see," was the answer shouted back. "Well, I wish you luck. Sorry you can't tell me all about it."

"You probably will know soon enough," replied Hal.

"Good. Don't want any company, do you?"

"No, I guess not."

"You want to be careful crossing the Balkans. I understand there are some British and French aircraft with the Serbians and Montenegrins. Look out for them."

"I'll be on guard," replied Hal. "Thanks for the information."

"Tell you what," said the Austrian, "I've been doing some scout duty there myself. I'll just trail along. May be able to help you out a bit"

Hal didn't think much of this plan.

"I can make it all right myself," he declared.

"Suppose you can," was the reply, "but it is just as well to be on the safe side."

"Well, suit yourself," said Hal, "but don't expect me to wait for you."

"If you can distance me you will have to travel," returned the Austrian.
"I've the fastest craft in the service."

"I'm glad to hear that," replied Hal, and added to himself: "I don't think."

"Set your pace," continued the Austrian. "I'll trail along behind."

"No use talking any more, I guess," Hal muttered to his friends. "May as well go along."

Chester and Colonel Anderson nodded their assent and the machine moved forward again.

Things might have gone well had it not been for Stubbs. Suddenly the little man uttered a yell and sat up straight in his seat.

"Ouch!" he shouted. "I've got an awful pain!"

CHAPTER II.

MONTENEGRIN MOUNTAINEERS.

Hal drew a sharp breath and tightened his hold upon the steering wheel.

There was no question 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 spinning 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