e came a sharp, throbbing roar of the airship motor in
motion. The propellers were being whirled rapidly about.

"Koku! Koku!" cried Tom, for he was still some distance off.
"Never mind them! Don't let the airship be taken!"

But Koku could only grunt. Big and strong as he was, half a dozen
men attacking him at once hampered him. He threw them from him,
one after another, and was gradually making his way toward the now
slowly-moving airship. But would he be in time?

Tom and Ned could not hope to reach the machine before Koku,
though they were running at top speed.

"Koku! Koku!" yelled Tom. "Don't let them get away!"

But Koku could only grunt--harder this time--for he fell heavily,
being tripped by a stick thrust between his legs. He lay for a
moment stunned.

"They're going to get away!" panted Tom, making an effort to
increase his speed.

"That's what!" agreed Ned.

Even as they spoke the roar of the airship motor increased.
Several of the dark forms which had been engaged in the struggle
with Koku were seen to pick themselves up, and run toward the
airship, that was now in motion, moving on the bicycle wheels over
the grass plot, preparatory to mounting upward in the sky.

"Stop! Stop!" commanded Tom. But it was all in vain.

The men leaped aboard the airship, which could carry six persons,
and a moment later, with a deafening roar, as the engine opened up
full, the big craft shot upward, taking away all but two of the
midnight visitors. These, who had seemingly been stunned by Koku,
now arose from the ground, and staggered off in the darkness.

"Get them!" cried Tom.

"We must see to Koku!" added Ned, "Look, there goes your airship,
Tom!"

"Yes, I know. But we can't stop that now. Let's see if we can get
a clue in these fellows!"

He pointed toward the two who had run off in the dark underbrush
surrounding the hangar plaza, and he and Ned trailed them as well
as they could. But from the first they knew it would be useless,
for there were many hiding places, and, a little way beyond, was a
clump of trees.

After a short search Tom gave up reluctantly, and came back to
where Koku was now sitting on the ground.

"Are you hurt?" he asked of the giant.

"My mind hurt--that all," said the big man.

"I guess he means his feelings are hurt," Tom explained. "Do you
know who they were, Koku?"

"No, master."

"But we must do something!" cried Ned. "They've got your airship,
Tom."

"I know it,"