“And what have you to do with it?” demanded Ivan loudly.

“Just this,” said Hal, and produced a revolver.  “Before I’ll stand for any more of this nonsense, I’ll put a hole through you.  Understand?”

Ivan looked at the lad, apparently bewildered, for some moments.  Then he said with a laugh: 

“Don’t you ever shoot at me with that gun.  Not ever!”

He rose to his feet and faced Hal threateningly.  The lad was nonplussed.  He had no idea that his bluff wouldn’t work.  He knew of course that he could never shoot the Cossack.

It was Chester who saved the day.

“Ivan,” he said quietly.  “That’s not your money.”

“What—­what’s that?” said Ivan, turning to him suddenly.

“I said that’s not your money.  Surely you are not a thief?”

“A thief?” cried Ivan.  “Who says I am a thief?”

“I do, if you touch the money in the bag you hold there,” said Chester quietly.

For a moment it seemed that the big Cossack would spring upon Chester; but the lad stood his ground, and suddenly Ivan sank down in a chair.

“No, I’m not a thief,” he mumbled.  “I’m not going to be a thief.”

He threw the bag of gold down heavily on the table and looked thoughtfully into space.

Chester approached him and laid a hand on his shoulder.

“There,” he said calmly, “I knew you wouldn’t.  This, you know, is the king’s money.  You wouldn’t touch that?”

“No,” said Ivan, then added hastily:  “but I have touched it.  I bought wine with it; and it wasn’t my money.”

His remorse was so apparent that Chester was forced to smile.

“Why, that’s all right,” he said.  “You are going to pay him back.  Now come with us.”

Again Ivan was silent for several moments.

“That’s right,” he said at last.  “I’m going to pay him back.”  He rose to his feet.  “Come, I shall go with you,” and they all passed out into the night.

CHAPTER XIX.

Into Serbia.

Two days later and we find our friends once more in the air and sailing swiftly toward the rising sun.

“Seems to me we should be along about there some place,” declared Hal, taking his eyes from the distance ahead for a brief moment.

“Unless you have not gauged your course accurately,” replied Chester.

“I’m sure I have made no mistake,” said Hal.

“Then we should be about there.”

“About where, that’s what I want to know,” put in Anthony Stubbs, from his place in the rear of the large army plane, the same in which the four friends had made their escape from the Austrians not so many days before.  “Where are we headed for, anyway?”

“That will be a little surprise for you, Mr. Stubbs,” Chester returned.

“I’m getting too old to care much about surprises,” declared Stubbs.  “In the first place, I have no business in this machine, anyhow.  I never was much good when my feet were not on the ground, and I feel pretty sick up here.”