And the farm hand, a heavy-set boy, eagerly fell in behind Frank and
Andy, as, after thanking Mr. Quackenboss heartily for his kindness they
passed out of the barn. Felix considered this an event in the tame
routine of farm life; and would be only too glad to stay up all night,
if necessary, in order to guard the precious aeroplane.

Once in the field, the boys explained to Felix what they wanted him to
do, and he promised not to meddle with anything connected with the
engine or the aeroplane itself.

They were passing back again toward the barns, having left their prized
possession in good shape, when Andy uttered a sudden exclamation that
told of both surprise and disgust.

"What's the matter now?" asked Frank, who had been talking with Felix,
and was hence not so wide awake as his chum.

"Just take a look over there, and see what's stopped on the road,"
remarked Andy.

"Seems to be a car, and I can see two heads raised above the top rail
of the fence, as if the people in it had sighted our aeroplane sprawled
out there in the field, and were wondering what sort of giant insect it
could be," Frank went on.

"Look closer, Frank," the other boy went on to say, while his disgust
deepened; "and you'll discover that the two fellows in that car happen
to be Percy Carberry and his shadow, Sandy Hollingshead. Did you ever
hear of such tough luck? Of all the boys in Bloomsbury they are the last
we'd want to know that we'd left our new hydroplane out, unguarded, all
night, in an open field. Guess I won't go home tonight, Frank. I'd
rather camp out here with Felix. You let my folks know, and turn up in
the morning with a new piece for that plane. That's settled and you
can't change it."

CHAPTER II

ON GUARD

"Perhaps I'd better stay with you, Andy," the other Bird boy remarked.

"No need of it," replied Andy, resolutely. "Besides, you know one of us
ought to get busy in the shop, making that new piece we really need so
that our job won't have to be done over again. You go, Frank. Perhaps
Mr. Quackenboss would let you have a horse; or if you cared to, you give
Percy a hail, and he'd take you back to town, I reckon. Goodness knows
he owes you a heap, after the way you saved his life the time he was
wrecked up on Old Thundertop."

What Andy referred to was a very exciting event which had occurred not
so very long before, and which was fully treated in the volume preceding
this.

Frank shook his head in t