Throughout the night Tim remained at the airport, supervising the installation of the radio detector in the fast biplane which Hunter provided for his use.
By dawn the plane was ready to go.
“What are you going to do now?” asked the managing editor.
“Start a steady patrol of the Cedar river valley,” said Tim. “When I get tired Hunter has agreed to relieve me. We’ll both ride the plane and only come down when we need gas and oil.”
“Won’t they get suspicious of what you’re up to?” asked the managing editor.
“I doubt it,” said Tim. “We’ll be up ten to twelve thousand feet all the time and with the muffler Carson has fitted on the exhaust they won’t be able to see or hear us on the ground.”
“And will the radio detector work at that height?”
“Giddings said it was good up to twenty thousand feet,” replied Tim. “At least it is the best we have and if it does work we’ll soon put an end to these marauders.”
An hour later the silver-gray biplane which they had equipped was cruising over the Cedar river valley. The altimeter showed 10,000 feet and Tim throttled down the engine as he started the patrol of the valley. Hunter, in the forward cockpit, had a headset on and was listening for some sound in the radio detector.
Through the hours of the morning they maintained their vigil and at noon flew halfway back to Atkinson to land at an air mail emergency field and refill their gasoline tanks.