om Swift got on their trail."

"But, just the same, they are afraid of him, and his searchlight,"
declared Mr. Whitford. "I guess they fancied that when they took to
airships to get goods across the border that they would not be
disturbed. But two can play at that game."

The talk became general, with pauses now and then while Tom swept
the sky with the great searchlight, the others straining their eyes
for a sight of the smugglers' airships. But they saw nothing.

The young inventor had just paid a visit to the pilot house, to see
that his wheels and guiding levers were all right, and was walking
back toward the stern of the ship, when he heard a noise there, and
the fall of a heavy body.

"Who's that?" he cried sharply. "Is that you, Koku?"

A grunt was the only answer, and, as Tom called the giant's name the
big man came out.

"What you want, Mr. Tom?" he asked.

"I thought you were at the stern," spoke Tom. "Someone is there.
Ned, throw the light on the stern!" he called sharply.

In a moment that part of the ship was in a bright glare and there,
in the rays of the big lantern, was stretched out Big Foot, the
Indian, comfortably sleeping.

"Here! What are you doing?" demanded Mr. Whitford, giving him a
vigorous shake.

"Me sleep!" murmured Big Foot. "Lemme be! Me sleep, and take ride to
Happy Hunting Grounds in air-bird. Go 'way!"

"You'll have to sleep somewhere else, Big Foot," spoke the agent
with a laugh. "Koku, put him down under one of the trees over there.
He can finish his nap in the open, it's warm."

The Indian only protested sleepily, as the giant carried him off the
ship, and soon Big Foot was snoring under the trees.

"He's a queer chap," the custom officer said. "Sometimes I think
he's a little off in his head. But he's good natured."

Once more they resumed their watching. It was growing more and more
wearisome, and Tom was getting sleepy, in spite of himself.

Suddenly the silence of the night was broken by a distant humming
and throbbing sound.

"Hark!" cried Ned.

They all listened intently.

"That's an airship, sure enough!" cried Tom.

He sprang to the lever that moved the lantern, which had been shut
off temporarily. An instant later a beam of light cut the darkness.
The throbbing sounded nearer.

"There they are!" cried Ned, pointing from a window toward the sky.
A moment later, right into the glare of the light, there shot a
powerful biplane.

"After 'em, Tom!" sho