“We must make sure that he’s alone, or else rouse the rest of the camp,” said Bud excitedly.  “Keep watch in every direction.  I’ll turn slowly and get a look at him, and then turn back and pretend not to see him.”

This program was observed carefully for a minute or two.  Meanwhile the spy crept closer and closer, crawling like a serpentine quadruped and making fairly good progress withal.  At last, however, Bud decided that it was time for him to do something to put a stop to this proceeding.

Without giving his companion any warning as to his intention, he lifted the catapult eye-line high, pulled back the sling, in which all this time he had held a stone nearly half the size of a hen’s egg, and let it fly.

Thud!

That the missile hit the mark hard was indicated, first, by the sound of the blow, itself, and, second, by the muffled cry of agony that followed.  The next instant the victim, who seemed to be struggling to retain his “quadruped balance,” rolled over with a moan of impotent agony.

CHAPTER XXVI

The Sling Shot Victim

“What’s the matter, boys?”

Mr. Perry appeared at the entrance of the tent with this question on his lips.  The boys turned quickly, while Cub’s father advanced nearer to pursue his inquiry.

“I shot somebody,” Bud replied.

“Shot somebody!” Mr. Perry exclaimed.  “What with?”

“This,” the boy answered, exhibiting his slingshot.  “Some fellow was prowling around here and I thought it was time to stop him.  He was standing in those bushes over there for a long time, and I suppose he thought he was fully concealed, but I saw him.  Then he started to crawl up close to the tent, and I let him have a good solid, heavy stone.  It went like a bullet—­these rubbers are awful strong, and I pulled them way back.”

“He isn’t killed; he’s crawling away,” Max interrupted at this point.

“We mustn’t allow that,” declared Bud.  “We must find out who he is and what he was up to.”

Just then Hal and Cub appeared on the scene, and a few words sufficed to explain to them what had occurred.  All of the campers on retiring had kept on their day clothes, in order that they might be ready for action in case of trouble in the night.

“Come on, we must stop him,” Cub announced.

This seemed to be the opinion of all, including Mr. Perry, and a general move was made in the direction of the slowly retreating injured spy.  They soon overtook him and threw a flood of illumination about him with their search-lights, which they had picked up in the dark almost as instinctively as a grandmother picks up her glasses in the morning.

“Why, he’s a boy!”

Bud was the only one present who gave utterance to this discovery aloud, but the “exclamation” flashed mentally in the head of every other youthful investigator in the group.  As Mr. Perry was not easily mystified, we must take it for granted that he was not easily astonished, so that probably he did not feel like giving vent to anything of the nature of an exclamation.