gon_?" said
Peggy, the next instant. "I mean that horrid looking man in the check
suit."

"I don't know. See, he has a monkey wrench in his hand, too," exclaimed
Bess.

Almost simultaneously the boys looked round from their work on the
biplane and saw the man. It was Lish Kelly. He was bending over the
engine and doing something to it with his wrench.

"Hey! What are you doing there?" yelled Roy.

"Just looking at your machine. No harm in that, is there?" demanded
Kelly, with a red face.

"None at all, except that we don't want our machines touched. How comes
it you have that monkey wrench in your hands if you weren't tampering
with the machinery?"

Jimsy spoke in a voice that fairly bubbled over with indignation.

"Don't get sore, kid; I wouldn't harm your old mowing machine. There
isn't one of mine but could beat it the fastest day it ever flew."

As he spoke Kelly slouched off. They saw him go up to a group of his
aviators and begin talking earnestly to them. Once or twice he motioned
with his head in their direction.

"So he _does_ mean mischief, after all," said Roy; "let's take a good
look at the _Dragon's_ engine. He may have injured it, although I don't
think he'd have had time to hurt it seriously."

They strolled over to the _Dragon_, with the girls trailing behind.

"Oh!" cried Peggy, as they came up, "look at that spark plug."

"What's the matter with it?" demanded Jimsy,

"Look, it's all bent and twisted out of shape."

"Jove, sis, so it is. Your eyes are as sharp as they are pretty!"
cried Roy.

"No compliments, please. Oh, that horrid man!"

"Who is he?" asked Jess. "You appeared to know him."

"Yes, we had some conversation with him this morning," laughed Roy; "but
to return to the spark plug; it's a good thing we carry extra ones."

"But we don't!" cried Jimsy, in a dismayed tone.

"What! you had a supply in a locker on your machine."

Jimsy looked confused.

"I've got to make a confession," he said.

"You didn't bring them!" cried Peggy.

"No, the fact is I--I forgot."

Jimsy looked miserably from one to the other. Here was a quandary
indeed. It might prove hard to get such a commodity as a spark plug in
Millbrook.

CHAPTER XVIII.

IN SEARCH OF A NEW PLUG.

It was while they were still discussing the situation that the
automobile with Jake at the wheel and Miss Prescott and The Wren in
the tonneau, drove into the grounds. What a difference there was in
the c