Soon after Don flew away with his younger chum, Garry was rejoined by the control assistant. They sat talking for some time: then, as Garry’s frequent trips to the balcony became noticeable, the man asked their reason and Garry explained their intention.

While he finished his story, the control chief, Vance, with Doc Morgan, came out from town, in the former’s car: soon afterward Mr. McLeod drove back from his trip with the mail.

The airport executive was in high spirits. When, however, Garry detailed his story, the face of Don’s uncle took on a serious look.

“Don knows nothing about helicopters,” he declared. “Besides, this isn’t the way to accomplish results. I have detectives watching. If you had given them all this information it would have been better than for Don to try to ‘show up’ the trick. That warns the real perpetrator, puts him on his guard. The detectives could probably have caught him.”

“That wasn’t the worst feature,” the control chief volunteered.

“The mail ’bus is due in half an hour,” he declared. “Suppose that hair-brained nephew of yours decides to ‘put on his act’ just as it is coming in?”

Startled, Garry saw the force of the argument.

“Don is going to have the helicopter over the airport till he gets a signal and gives one,” he asserted. “I’ll signal him to come down, to give up the idea.”

Then, as another thought came to him, he added:

“I’d better get the Dragonfly warmed up and on one of the outgoing runways, sir. If anything should compel Don to land in the bay or the swamp—or if he didn’t recognize my signal—I could manage to fly the ‘crate’ that far—I’ve had fifteen hours solo in her.”

To that the others agreed, including the private detectives summoned from various posts about the airport where they were on watch.

With the help of the night mechanician, Garry got the Dragonfly out and set its engine going.

Then he hurried back to the control tower, to discover that the landing had been made by the Dart, as the flare had revealed.

Then there was silence, and alert, but futile watching, until Garry, watching the Northern skies, discerned the approach of the helicopter, as it swung along above the clouds, between two of which its light pontoons showed for a second.

Garry rushed to get a strong electric torch.

“I’ll send a blink-signal in Morse code,” he told Don’s uncle.

Waiting until the helicopter drifted down, he sent the signal which Don and Chick misinterpreted.

From that moment onward, all was confusion.

Garry rushed, with Mr. McLeod, to the Dragonfly, and prepared to take off.

The signal man in the control tower, watching the sky, sent them a triple flicker of the pilot’s spotlight, agreed on as a sign that the mail ’plane was in sight.

Then came the delay that was caused by Garry’s great excitement, so that he did not get the Dragonfly off the runway at the first attempt.

Instead, holding the elevators down too long, he got too near the end of the runway to risk trying to climb above some wires that ran in a diagonal line across the space ahead. Easily cleared in a correct take-off, they might have been the means of snagging the underbody with Garry’s slight experience in climbing angles and control manipulation.

The Dragonfly, just at the end of the runway, had to be turned, taxied back, and given a fresh start.

As he topped the wires on his second attempt, Mr. McLeod prodded Garry. The young, inexpert pilot, cutting the gun, and, fortunately retaining presence of mind enough to drop the nose to a glide as he cut power, looked around.

The man in the second seat pointed aloft.

In a quick look Garry took in the situation.

Fearing the worst, he seemed to sense its imminent arrival.

There, above the edge of the bay, a cloud was glowing. From his point of view he did not see the flickering picture, but he guessed it was either there or soon to appear.

He gave the nose a tilt upward, opening the throttle, as he saw the edge of the marsh seeming to rise up toward the Dragonfly.

As soon as he had climbed to a safer level he looked again.

There was the mail ship, coming down!

He again cut the gun for a glide, the better to watch.

His heart was in his mouth.

The mail ship was dropping swiftly. Suddenly it side-slipped.

Would there be a crash?

“Poor Don!” gasped Garry, “he has sewed himself up in an awful snarl if anything happens!”

At the same instant that the siren began to scream its crash summons he saw the mail ’plane come out of the side-slip.

To his amazement its pilot did not appear to be aware of the Dragonfly, cruising in a gently banked circle over the edge of the swamp, just beyond the end of the runways.

Instead, with a spiral, the pilot began to climb.

The beam of the airport searchlight flashed into being, and as it swung past that mail pilot, Garry, his head turned over his shoulder, caught sight of the pilot’s arm upraised, his fist clenched, being shaken furiously toward the upper air into which the mail pilot climbed.

“He’s wild with anger!” Garry decided.

He tilted his elevators to lift the Dragonfly, full power being on as he made as steep a climb as he dared.

He must get above the clouds.

If he could reach the altitude in time to signal Don to descend, the young pilot in the helicopter might avoid that sinister vengeance so clearly planned by the irate pilot of the mail craft.

Clearly Garry saw that the man had been anticipating some manifestation of the haunting spectre, had planned a deliberate reprisal.

Justly, as Garry realized, he proposed to take into his own hands the vengeance due for the terrible menace of the evil apparition.

“But—it’s Don—and his intentions were perfectly innocent!” Garry muttered, trying to edge the throttle a notch further on.

The clouds were just above him. He made his climb into a banked, turning ascent, passing through the thin edge of a fluffy vapor, to come out into the clearer air on a level with Don.

Already the young pilot was descending.

But this was not evident to the infuriated mail pilot who, coming straight at the helicopter from a swing on wingtip at a higher elevation over the swamp, made a ferocious dive, on wings of vengeance, for the ungainly ship Don piloted.

His intent was clear.

With his “propeller wash,” or slip-stream of turbulent air, he meant to upset the helicopter.

Garry held his breath. He could do nothing.

The mail ship passed just behind the helicopter.

It wavered, tossed, bent far to the side—began to go down—fast!