"Oh, Bob, don't be such a grouch," protested Jack. "What if nothing
comes of it? We'll have had a good trip, anyhow."

Bob grinned.

"I'm not grouching, Jack," he said. "Only I wanted to see what you had
in mind. If it's just a flying trip you're after, well and good. I'm
with you. The plane is limbered up since I worked it over, and
yesterday's little spin gave me a taste for more, too. But if you are
really intent on getting at the bottom of this mystery, I have a
proposal, too. What's the matter with our hunting up the Secret
Service men? Maybe they would be glad of our tip."

"Good for you, old ice wagon," cried Frank, slapping his chum's broad
shoulder.

Jack likewise nodded approval. The previous summer the boys had been
instrumental in thwarting the plots of an international gang on the
California coast to smuggle Chinese coolies into the country in
violation of the Chinese Exclusion Act. As a consequence, they had
made the acquaintance of Inspector Burton of the Secret Service and
had even been called to Washington to receive the personal thanks of
the Chief for their service and to be introduced to the President.
Their adventures during that exciting period are related in "The Radio
Boys on Secret Service Duty."

"Very good," said Jack, bounding to his feet. "Come on, let's go. It's
ten o'clock now. If we hurry, we can cover the sixty miles to Mineola,
put up the plane, and be in the city by noon. That will give us two or
three hours there, and we can be home easily in time for dinner."

"All right," said Bob. "I'll tell Della where we are going, in case
Mother isn't up yet. She had a bad headache, and may be staying in
bed. You fellows go down to the hangar, and start getting out the
plane. I'll join you right away."

Jack and Frank hurried away, while Bob went to execute his mission.
When he rejoined them at the hangar, the plane already was on the
skidways.

"You take the wheel going up, Bob," said Frank. "I'll pilot her
home."

The trip to Mineola flying field, where Bob and Frank and Mr. Temple
as well had taken their flying lessons, was made without incident.
Planning not to arouse the suspicions of anybody who might be on
watch, Bob was careful to steer a course over the water a good mile
out from Starfish Cove. Watching through the glass, Frank reported the
little plane missing and no sign of life on the tiny beach or in the
woods beyond where the radio plant was hidden.

Mechanics at the