“I’ll take the controls this afternoon,” said Hunter, and Tim agreed to the suggestion.
When they were near the valley again Tim set the radio detector going. There was a low, steady hum in the earphones for the noise of their own motor was cut out of the set’s pickup.
At two o’clock a sound came through the earphones that electrified Tim. Hunter, in the rear cockpit, could see Tim’s body tense as the flying reporter bent over the detector and adjusted the dials for more delicate tuning.
Somewhere below them the motor of a powerful plane was being warmed up!
The roaring in the earphones was strong; then weak, as their own biplane swung away from the source of the sound. By following the path of the strongest sound they would be able to find their quarry and Hunter watched Tim’s hand carefully for directions on how to pilot the plane.
When they reached the center of a dense forest along the right bank of the Cedar the roaring was loud and steady. They were still up eight thousand feet and too high to see what was going on below. Tim took a pair of field glasses out of a case and leaned over the side of the ship while Hunter banked the biplane in easy circles.
The powerful lenses made the ground leap toward them and Tim could see every object clearly. He gasped as his glasses focused on a clearing in one of the densest parts of the forest.
He was looking down on an exact replica of the plane he had seen in the makeshift hangar in the Jersey woods only two days before. The upper wings, as he had expected, were carefully painted so that detection from the sky was almost impossible.
Under normal conditions Tim and Hunter could have flown low over the clearing without seeing the plane but thanks to the radio detector they had been able to spot it with little trouble.
Hunter shut off the motor and leaned toward Tim.