"Hum!" mused Mr. Swift. "Well, are you going to do it,
Tom? Seems to me you ought to take a rest. You haven't been
back from your gold-hunting trip to Alaska long enough to
more than catch your breath, and now--"

"Oh, he doesn't have to go in this right away," eagerly
explained Mr. Gunmore. "There is plenty of time to make a
new craft."

"Well, Tom can do as he likes about it," said his father.
"Do you think you could build anything speedier than your
Butterfly, son?"

"I think so, father. That is, if you'd help me. I have a
plan partly thought out, but it will take some time to
finish it. Still, I might get it done in time."

"I hope you'll try!" exclaimed the secretary. "May I ask
whether it would be a monoplane or a biplane?"

"A monoplane, I think," answered Tom. "They are much more
speedy than the double-deckers, and if I'm going to try for
the ten thousand dollars I need the fastest machine I can
build."

"We have the promise of one or two very fast monoplanes
for the meet," went on Mr. Gunmore. "Would yours be of a
new type?"

"I think it would," was the reply of the young inventor.
"In fact, I am thinking of making a smaller monoplane than
any that have yet been constructed, and yet one that will
carry two persons. The hardest work will be to make the
engine light enough and still have it sufficiently powerful
to make over a hundred miles an hour, if necessary.

"A hundred miles an hour in a small monoplane! It isn't
possible!" cried the secretary.

"I'll make better time than that," said Tom quietly, and
with not a trace of boasting in his tones.

"Then you'll enter the meet?" asked Mr. Gunmore eagerly.

"Well, I'll think about it," promised Tom. "I'll let you
know in a few days. Meanwhile, I'll be thinking out the
details for my new craft. I have been going to build one
ever since I got back, after having seen my Red Cloud
crushed in the ice cave. Now I think I had better begin
active work."

"I hope you will soon let me know," resumed the secretary.
"I'm going to put you down as a possible contestant for the
ten-thousand-dollar prize. That can do no harm, and I hope
you win it. I trust--"

He paused suddenly, and listened. So did Tom Swift and his
father, for they all distinctly heard stealthy footsteps
under the open windows of the library.

"Some one is out there, listening," said Tom in low tones.

"Perhaps it's Eradicate Sampson," suggested Mr. Swift,
referring to the eccentric colored man who was employed by
the inventor and his son to help around the place. "Very
likely it was Eradicate, Tom."

"I don't think so," was the lad's answer. "He went to the
village a while ago, and said he wouldn't be back until late
to-night. He had to get some medicine for his mule,
Boomerang, who is sick. No, it wasn't Eradicate; but some
one was under that window, trying to hear what we said."

As he spoke in guarded tones, Tom went softly to the
casement and looked out. He could observe nothing, as the
night was dark, and the new moon, which had been shining,
was now dimmed by clouds.

"See anything?" asked Mr. Gunmore as he advanced to Tom's
side.