Mortlake started and paled.  Then, without vouchsafing a reply, he strode off in the direction of the farm house to get the water he needed.

“Now, Mr. Bradbury,” said Roy, extending a hand.

The young officer leaped nimbly into the chassis, and presently a buzzing whir told that the faithful Golden Butterfly was taking the air once more.

“Score two for us!” thought Peggy to herself.

From a far corner of the pasture, Mortlake watched his young rivals climbing the sky.  He shook his fist at them and his heavy face darkened.

CHAPTER XI.

THE MARKED BILL.

Some two days after the events narrated in our last chapter, Lieut.  Bradbury, sitting in the library of the New York Aero Club, on West Fifty-fourth Street, received a telegram from Eugene Mortlake.  He was considerably astonished, when on tearing it open, he read as follows: 

“Must see you at once.  Have positive proof that young Prescott is about to sell out his secrets to foreign government.”

“Phew!” whistled the young officer.  “This is a serious charge.  If it is proved, it will bar Prescott from bidding for the United States government contract.  But I can hardly believe it.  There must be some mistake.  However, it is my duty to investigate.  Let’s see—­three o’clock.  I can get a train to Sandy Beach at four.  Too bad!  Too bad!”

The young officer shook his head.  He had come to have a sincere regard for Roy and his pretty sister, as well as admiration for their resourcefulness and pluck.

When it is explained that during the time elapsing between his lucky lift in the Prescott machine and the reception of the note, that Lieut.  Bradbury had notified Roy that he would be expected to report at the Brooklyn Navy Yard, his feelings on learning that there was suspicion directed against his young protege, may be imagined.  Mortlake, too, had received a notice that his machines were eligible for a test, so that there would have seemed to be no object for his acting treacherously.  Otherwise, the young officer might have been suspicious.  What he had seen of Mortlake had not particularly elevated that gentleman in his opinion.  But if he had desired to wrong the Prescotts, reasoned the officer, such a resourceful man as he had adjudged Mortlake to be, would have sought a deeper and more subtle way of going about it.

“And I’d have staked my word on that boy’s loyalty; aye, and on his sister’s too,” muttered the officer, as he made ready for his hasty trip to Long Island.

By this it will be seen that Lieut.  Bradbury was by no means proof against the rather common failing of inclining to believe the first evil report we hear.  It is a phase of human nature that is not combatted as it should be.

In the meantime, Roy and Peggy had sustained a surprise, likewise.  The day before that on which Lieut.  Bradbury received the disturbing dispatch, an automobile had whizzed up to their gate and stopped.  Roy, Peggy and Jess and Jimsy were at a game of tennis, when a rather imperious voice summoned them, from the tonneau of the machine.