his several airships. In front of it was a big, level grassy
space, needed to enable the aircraft to get a "running start"
before they could mount into the clouds.

"See anything of Koku?" whispered Ned.

"No," answered Tom, in the same cautious voice. "I guess he must
be hiding--"

"There he goes now!" hissed Ned, pointing to a big figure that was
approaching the hangar. It was undoubtedly that of the giant, and
he could be seen, in the dim light, stalking cautiously along.

"I wonder where the uninvited guests are?" asked Tom.

"Probably in the airship shed," answered Ned. "Koku was after them
as soon as the alarm went off, and they couldn't have gotten away.
They must be inside there yet. But what can their game be?"

"It's hard to say," admitted Tom. "They may be trying to get
something belonging to me, or they may imagine they can pick up
some valuable secrets. Or they may--" He stopped suddenly, and
then exclaimed:

"Come on, Ned! They're after one of the airships! That's it! My
big biplane is all ready to start, and they can get it in motion
inside of a few seconds. Oh, why didn't I hurry?" he added,
bitterly.

But the hangar was still some distance away, and it would take two