“Hold on,” said the cooler one, raising his hand; “it’s true that the canvas of the planes has been spoiled utterly; but if that was the whole thing I wouldn’t care so much. Let me examine the engine first.”

Eagerly he removed the canvas covering the motor. Andy went and opened the great doors wider, so that he could have an abundance of light. Then, with his heart in his throat, so to speak, Andy hovered near, waiting for the dread verdict.

Presently Frank looked up.

“Oh!” cried the other, as he saw that his cousin was smiling, “tell me nothing vital has happened, Frank! They didn’t dare hurt that little darling Kinkaid engine, did they? No, your beaming face tells me so. Is that all the damage they did?” and he pointed to the cut canvas of the two planes.

Frank nodded his head.

“I can’t find anything more, old fellow,” he said, cheerily, the cloud dissipated from his brow that had a minute before been so threatening.

“But how did that come, d’ye think?” demanded Andy. “Seems to me I can give a right good guess who did this dirty job, even if they covered up their tracks like they always do; but why would they stop at smashing our planes, when they could put our engine on the blink so easy?”

“Well,” observed Frank, thoughtfully, “we happen to know that some people I won’t mention have more than their share of caution. While we mightn’t make much fuss about the planes, if the engine had been tampered with we’d be apt to complain to the chief of Bloomsbury police, Mr. Waller, and have him investigate.”

“But what could have been their object?” Andy complained, as he looked closer at the slashed material covering the framework of the planes.

“Just malicious deviltry, I guess,” replied Frank, gloomily. “They were curious to see what we were doing with our monoplane, and forced the lock last night. Then the temptation was too great to be resisted. They just had to do something to satisfy that craving for ugliness. Besides, don’t you see, it would delay us; and that would allow them to steal some of our thunder.”