Jerry, as Carlito paused. "How did the Thunder Bird knock those chaps around that way?"

"Search me," responded the Apache. "He says the Thunder Bird was angry at having his shrine profaned with blood and wouldn't let it be used again."

"Sounds a whole lot like the Thunder Bird was after them sheep, Herb," laughed Dunk. "Better get us medicine men's outfits, Carl! We may need 'em!"

"I think we'll need six-guns more," replied the Apache gravely.

"Gee, it's goin' to be a real adventure," exclaimed Fred, his bright eyes snapping. "But how are we goin' to start?"

"Well, if the Thunder Bird lives up in the mountains, why not try and find out where he roosts?" suggested Herb.

"Anyhow, while we're waiting for our uniforms, we might take Fred on a little hunting an' fishing trip up in the mountains, and mebbe do some investigating on the side," added Jerry.

"And talk over how we're goin' to get at the sheep stealer," went on Fred.

So it was decided that on Monday the boys would go for a hunt and map out their plans. But they did not know what was to happen in the meantime to help solve the problem for them.

CHAPTER IV

AN AVIATOR APPEARS

"Hello, who's that talkin' to father?" exclaimed Jerry next morning as he and Fred came back from the range where they had been having a target contest to try out the service revolvers Captain Crawford had lent them.

Captain Crawford called the boys over and introduced the stranger, a tall, trim-built young man, as Mr. Hawke.

"I'm sure you boys will like Mr. Hawke," he said. "He's from the military aviation school at Fort Omaha, and knows how to build aeroplanes."

This was enough to make the boys look upon Hawke as a friend and hero, even if he hadn't smiled encouragingly and held out his hand.

"I'm sure I'm going to like you too, boys, and I'm glad to know you're interested in aviation. I always like to see boys up-to-date."

The boys hardly knew what to say to such a warm greeting as this, but Fly put in his appearance at that moment and saved them from further confusion.

"Come on over here, Fly," called Jerry.

"He's just crazy about airships," he explained, turning to Mr. Hawke.

"Then I want to meet him," said the aviator, his genial face lighting with a smile.

"I'd rather meet you then Santa Claus," exclaimed Fly, enthusiastically, feeling at home at once with the newcomer, and experiencing none of the embarrassment of the other boys. "I hope you're goin' to stay."

"Well, I'm planning to spend my vacation here. I didn't expect to arrive so soon, but some friends were coming this way, so I dropped in unannounced."

"We all like this kind of a surprise," assured the captain, just as Dunk Rivers came up and said he was wanted on the telephone.

"I guess I can leave you with the boys, Hawke," said the captain, after introducing Dunk.

"You bet. I like boys—especially aeroplane boys."

"Maybe you can give them some pointers about the mystery at the Phipps ranch," Mr. Crawford called back as he hurried away.

"We'll tell you about that," volunteered Jerry, in answer to Mr. Hawke's look of inquiry, and, assisted by Fly, Dunk and Fred, he told the story of the runaway and the loss of sheep at the ranch.

"And this trouble has been going on about a month?" asked Mr. Hawke. "Looks to me as if your Indian friend is pretty near right. It must be some kind of flesh-eating animal or bird that is doing the damage. So you boys are going to trail him down?"

"That's the idea," answered Dunk.

"We've formed a Boy Scout Patrol," continued Jerry; "ordered our uniforms an' everythin'. Fred's leader."

"Splendid," exclaimed Mr. Hawke heartily. "I used to be scout master of a bunch of fellows down at Fort Omaha, but my work got so pressing that I was obliged to give it up. I enjoyed it though."

"Gee, that's fine. Glad you're goin' to stay all summer," exclaimed Fred.

"How are you going to carry on this hunt?" asked the aviator.

"We haven't just decided yet," replied Jerry. "Got to figure that out."

"If it's a bird it seems to me you ought to have an aeroplane," suggested Mr. Hawke, his eyes twinkling as he watched for the effect this would have on the boys.

"It would be just the thing," cried Fly.

"Of course," chimed in Dunk. "We could fly right after him then."

"That would be the way to do it," said Mr. Hawke, pleased with their enthusiasm. "Can't you manage to build a machine here at the fort?" he added.

"Mebbe Mr. Phipps would help us out," cried Fly at once, taking the suggestion seriously.

"That's right," assented Jerry gravely.

"But we don't know nothin' at all about it," said Dunk.

"Well, you boys come up to my room to-night," responded Hawke. "I'll show you something you'll be interested in. Come along and bring your friends. I suppose there are some other boys around here."

"You bet; three more in our crowd. They're all bugs on aviation too," Dunk assured him. "We want to get the Boy Scout aviation badge."

"Bully for you. That's the kind of talk I like to hear." Hawke gave Dunk a friendly slap on the shoulder. "Now, I'm going to spend the afternoon with your father and Captain Crawford. Good-bye till to-night."

"Ain't he a peach?" exclaimed Fly, when Hawke was out of hearing.

"He's a looloo! Gee, this is luck. Aviator—scout master—everything nearly," agreed Jerry warmly.

"Wonder what he's going to show us to-night," queried Fred.

"Mebbe he's got some more ideas about the Thunder Bird that he didn't tell us," suggested Dunk.

"He's a prince anyway," Jerry exclaimed. And in this all the boys agreed.

Fly had to go back to his work, and it was decided to call up Herb Phipps and Tender Gray, telling them to come over that evening on the aviator's special invitation. Dunk said he would notify Carlito.

At eight that night all the boys met at Jerry's and went together to Mr. Hawke's quarters on the third floor of the old barracks. Graystock wore his tenderfoot badge, while Fred had pinned on all his medals, including the one for aviation.

Carlito, Herb Phipps and his cousin edged into the room somewhat timidly, but the aviator's cordial greeting caused them instantly to forget their embarrassment.

"I'm glad you managed to round up the bunch," Hawke said, after the new trio had been presented. "This lesson won't have to be repeated. And," he continued, observing Fred's decorations, "all of you scouts ought to be wearing aviation badges soon. That is, if you give careful attention to what I'm going to tell you."

"We'll listen, all right," promised Fred. "That's what we're here for."

Hawke smiled. "That reminds me. You fellows came pretty near missing the surprise I've got for you. When Ike went down to Silver City they told him my trunks hadn't come. He waited, however, and they arrived on the next train. He delivered them only a few minutes ago."

The boys exchanged glances of inquiry. What had Ike and the trunks to do with it?

But Hawke soon answered them by pulling a large steamer trunk into the center of the room.

"Get down here," he said, throwing back the top. The boys gave a gasp of surprise and were down on their knees beside him. Lying in the trunk were the parts of a miniature aeroplane.

"Now, scouts," said Mr. Hawke, amused at their excited exclamations, "we'll put this together, and I'll show you the model of the 'Thunder Bird Aeroplane.'"