Taking off into the July south-wind, Don waited only long enough to observe the regulation compelling an airplane to be well beyond the airport limits before turning. Then he began a turning climb to nose into the East, crossing Long Island.

Although their course did not take them near the swamps which had been so closely connected with their mystery—or mysteries!—Don glanced in that direction.

Garry, behind him, busy adjusting the tube of the student’s communication helmet by which he could talk to Don, did not see what the pilot noted. Don shook the ship gently. Garry looked up.

Chick, behind them, getting a life belt inflated from an air bottle, because this would be a part of the mail flight requiring him to run a slight risk of immersion in the sea, looked up at the same time.

Don’s hand, waved toward the swamps at the left wingtip, as they came around, saw a curious object over the swamps.

They were too far away to note it with much certainty; but Garry was sure that the queer, ungainly thing rising steadily into the air was one of the aircraft whose horizontal blades, above the fuselage, enabled it to take off and rise without first attaining the flying speed required by an ordinary airplane. Its huge propeller blades acted both as power and support surfaces.

“An auto-gyro,” Garry said into the helmet communication tube.

Don shook his head.

“What did you tell him?” Chick bent far forward to shout to Garry.

“Said it was an auto-gyro!”

“No!” Chick had sharp eyes. “It isn’t the modern kind, anyhow. It’s what they call a ‘helicopter,’ Garry.”

Garry looked a second time, carefully.

“Chick’s right,” he murmured to Don. “He says it’s a helicopter—it has the lifting blades that let it rise straight upward and then it has a ‘tractor’ propeller forward that sends it through the air horizontally. It can go higher by giving the horizontal blades more speed, stay almost stationary by adjusting speed, or settle lower by slowing the blades. The tractor prop gives it forward speed. Chick’s right.”

Don nodded. That had been the reason he shook his head, to correct Garry’s terminology, because all the more modern auto-gyros he had seen employed an adjustable-angle horizontal set of blades for both upward and forward speed, and had refined the tractor propeller at the nose.

“But what is a helicopter doing over the swamp?” he wondered, “and where did it come from?”

With a meeting arranged between the amphibian Dragonfly and the big trans-Atlantic liner, there was no time to investigate.

“Does that helicopter have anything to do with the mystery?” Garry spoke through the Gossport tube.

Don could not give an answer.

“It might,” Garry continued. “Only I don’t see just how. The spook ships we saw come together in the sky were old-fashioned biplanes. They weren’t real, either, because you flew right into the cloud, Don.”

The pilot nodded. Their speed rapidly took them Eastward, and away from the swamp; but as he set his course, bearing slightly North, crossing one of the Island’s flying fields at a good altitude and with Barren Island’s new Bennett field back of the right wing’s trailing edge, he puzzled his brain a great deal about that strange ship rising from the swamps. Why was it there at all? Had it been forced to settle there? Or—did someone keep it there? If so, he thought, for what purpose?

“With the airport so handy, nobody would store a helicopter anywhere in a mucky swamp,” he decided. “It must have been a compulsory landing.”

With the lights of Coney Island, far to the right, and of Long Beach, and the Rockaways showing their Summer activities more nearly under the trucks, Don nosed out over the sea.

There he opened the throttle almost full-gun.

They must meet the liner as far out as possible. The fuel supply had been calculated to take them a hundred and thirty miles out and back with the essential safety reserve; Don had a notion to stretch that distance a trifle, because every mile the airplane saved the ship before the return would mean that much more rapidity in bringing in the mail.

Many ships came up over the horizon, were passed, and receded behind the tail.

Chick’s sharp eyes first discerned the special signal carried for the occasion by the liner they sought to meet.

“Good work,” Garry commended as Chick poked him three times and indicated the tiny trio of white lights set above a blue one on the masthead of the approaching boat, just coming up, it seemed, over the horizon line.

He gave Don the position. The youthful pilot shifted rudder and altered the course somewhat, gunning up to full speed.

“We will meet her ten miles further out then we expected to,” he murmured, pleased. That would mean faster time back for ten miles more of the distance from shore, and ten miles at their speed as contrasted to ten miles at the liner’s best, compensated for the difference in rapidity of flight between the Dragonfly and the faster Dart that could not make the flight.

They bade fair to establish a mail ship-to-shore record.

Chick sent over the flash-rocket that signalized their approach.

The vessel’s searchlight leaped to life, probed for and touched their wings, darting swiftly aside to avoid blinding the pilot.

The liner came on at full speed. Don dropped the nose, cut the gun and approached at an angle calculated to bring down the amphibian to the water at a point near, to one side of, and just ahead of the course the liner pursued.

The vessel’s lights looked beautiful, seen from the air. Chick and Garry thrilled to the wonderful spectacle. Don’s elation came more from the precision movements with which the mail pouches, buoyed with a self-igniting water flare on the buoy, went over side in the glare of the liner’s searchlight.

Calculated with skill, favored by good control, Don’s line of descent set the amphibian’s pontoons on the fairly smooth sea in a line that sent the liner sweeping by his wingtip with not a dozen yards to spare.

Tossing by in her wake, the buoyed pouches, accentuated by their marking light, were in a direct line with the airplane’s course.

Garry motioned to Chick.

His part was to clamber to the strut, cling to a bracing wire, catch up the light buoy.

Garry’s office was that of observer, to align Don’s maneuvers with Chick’s activity. Don had done well, so far: Garry would give him all the aid he could to complete the maneuver.

Seeing them safely past, though shaken by the ship’s turbulent wake, the man at the searchlight swung it onto their tail, to give Chick all the light possible.

Chick saw the buoy bobbing closer.

“A point to the right, Don!” Garry called into his tube. “He can’t quite reach—that’s better!”

An instant later he spoke again.

“Cut the gun, Don!”

The Dragonfly, skittering along on the top of the moiling wake began to settle into it, more shaken than before by the immersion into a swirl of cross-currents; but the instant of delayed speed was all that Chick required.

His outreaching hand stretched on straining muscles.

Fingers alert and agile gripped the rope bound around the buoy.

“Full-gun, Don!”

Up, and out of the danger of an upset, with engine roaring, they rose.

Chick, clinging to the mail pouches, held on.

Garry, stretching out his arm, as Chick swung inboard, caught the buoy and gave Chick the use of both hands to cling in the increasing blast of air caused by the climb.

Almost, for an instant, Chick’s heart fell into his flying boots: spray-wet, a wire slipped in his grasp!

“Cut!” Garry called to Don.

Leveled, with power reduced, the ship, for an instant, lost its climb and barely held safe margins of forward momentum.

In that instant Chick mended his grip, catching a strut.

With the mail pouches drawn to the cockpit floor, with Garry, his hands free, aiding, Chick got quickly and safely back to his place.

“Oh-kay!” he shrilled, delightedly, as he snapped on his safety belt.

Gunning up at Garry’s relayed signal, Don made his climbing turn.

They were pointing straight for the airport when he revved up to his full power.

The mail flight would be a success.

All they had to do was to fly straight, top speed, set down and be applauded. They need not cross the swamps of so much mystery and fear. They could come in from the East, landing sidewise to the wind. Don flew the distance to the point where they sighted the airport with his heart singing to the tune of singing wires, laughing with the purr of the motor. The successful termination of the mail flight was in sight.

Then the mystery helicopter struck!