Straight and true Don sent the swift, light Dart to its mark.

Over the swamp they had last seen the helicopter.

In the half hour that had elapsed it could, of course, be far away. “But I don’t believe it is,” Garry murmured into his Gossport tube.

Don, listening, agreed with Garry’s surmise.

“Did you notice how that Thing looked while Chick’s flare burned?” Garry continued his conversation. “Under the big, bulky body, the helicopter had two things jutting out—I think they were pontoons. They have some sort of special bracing, and shock absorbers, so it can set down on land; but I am sure that the two projections were pontoons—and that, Don, tells us that the helicopter can get down on the water just as easily as a regulation amphibian.”

Don agreed as he watched the horizon line ahead.

“That Thing is human,” Garry added. “Ghosts don’t set off rockets.”

Once more Don was in full agreement.

They scanned the dark, silent sky around them and ahead of the nose as they approached, on swift wings, the scene of their recent struggle to escape annihilation and to get the mail in on time.

“Not a thing in sight!” Garry checked Don’s decision.

Where had the mystery ship gone?

As he asked the question, Garry removed the speaking tube from his lips and bent his eyes downward, over the cockpit cowling.

He searched the unrevealing water, grass and ooze of the swamp.

“Don!” his lips were again at the tube, “forward of the right wing, just where the fifth brace connects to the leading edge covering, I see a little light flickering. There—the wing is over it. Look! In a second it will be just at the trailing edge—there it is!”

Don saw the flicker.

As he started downward in a tight spiral, to keep close over the area and get lower, Garry spoke quickly.

“No, Don!” he objected. “Stay high, and go on away. Then we will climb higher and come back.”

Don took the ship out of the tight spiral, but turned his head inquiringly.

“It might be a lure!” Garry explained.

Don saw the logic of his chum’s reasoning: if the Demon, as he thought of that strange occupant of the helicopter, wished to draw them down into a trap, it—or he—would chose such a ruse.

Don, lifting the nose, soared away, climbing.

A mile away he banked around, and returned.

“There it is, again!” Garry, observing, indicated the flicker. It was more vivid than the intermittent glow of marsh gas which they saw in spots where rotted vegetation gave off its luminous aura.

“He is trying to lure us down, I’m sure,” Garry declared.

Adjusting the controls so that the ship, well-balanced, flew itself for a moment, Don scribbled a note, passing it to Garry.

“I don’t know,” Garry responded, reading and considering the communication. “It might be safe and it might not to go down. I know we can’t get anywhere flying around up here; but anybody as deadly as that Demon is dangerous to get close to.”

Don hesitated.

He wished to beard the deadly one in his lair, to come to close grips; he did not desire to risk Garry’s safety without his chum’s consent.

Nevertheless that was what he had asked for a volunteer to help him with.

Garry, he knew, was cautious, not cowardly. Therefore Don hesitated.

Once more Garry’s steady voice came to his ears.

“How about doing this?” Garry asked, “let’s fly away as though we hadn’t seen the lure, get over the airport, and signal by blinking the flying lights. The Demon can’t read them that far off, and we won’t be dropping flares to warn him. We can tell Chick we have located our ‘bad man’ and he can get your uncle, with the police, to surround the marsh. Then we can start sending over flares, go down, and guide the officers. They will catch the Demon if he runs, and, by closing in on all the paths, he can’t get away.”

Don agreed by switching the nose quickly in the proper direction.

Over the control tower they made a glide.

With the flying lights snapping on and off, Don spelt out a signal to Chick as he held the Dart in a tight, banked circle.

No response came, the control tower remained unresponsive. Its pilot signal beam, a small spot, did not flicker on and off to spell the “O. K.” Don expected from his watching chum.

Chick, as a matter of fact, was otherwise occupied.

“Let’s set down,” Garry suggested. “The Demon will probably wait, hoping we will go over again and see his lure. He must have meant us harm or he wouldn’t have set those rockets to strike the Dragonfly.”

Don, flashing the “must land” signal of distress with his blinking flying lights, got no response: he decided to risk approach without the signal, and finally tumbled out of the Dart with Garry already on the ground.

Leaving the Dart idling, slipping chocks under the wheels, Don and Garry hastened into the big main hangar.

It was empty, echoing, deserted.

So, too, they found the upper offices.

“There has been an awful ‘shindy’ in the designing department,” Garry whispered, training his finger, at the door, after flashing on the office lights. “Somebody has tried to break into the locked cabinets, and there is a wastebasket turned over and a chair upset. There must have been a fight in there.”

Don, looking, agreed.

“Come on!” he muttered, “something has happened here. Uncle is in New York, of course. He hasn’t had time to get back from delivering the mail we flew in. But where is the control room crew, and the hangar man, and Doc, and—Chick?”

Up the stairway, not replying, Garry followed him.

“Nobody in here!” Don turned a dismayed, and frightened, look on his chum, who responded with equal concern in his face.

“Something has happened,” whispered Garry.

At once he became practical.

“Don, we can’t stay here to find out what’s wrong. You want to capture the Demon. Run down and check your fuel, while I telephone the police station and report this—and ask for help on our ‘round-up.’”

Don raced back down the stairways.

Garry, rejoining him, a scant ten minutes later, was very sober.

“Chief wasn’t at the station,” he reported. “Man at desk seemed to be half asleep. Said the Chief had been called away on a special errand. Wouldn’t say how soon he could get help out here. There’s a mystery about all this, Don. What shall we do?”

“Run up and leave a note for Uncle,” Don counseled. “I’m filling the tank. If we can’t get help, we’ll handle this ourselves!”

“How?”

“I’ll go aloft, fly over the swamp, locate that area, and act as if I have discovered the lure for the first time, if it is still there.

“And I think the Demon is waiting, sure we’ll take his bait!” he added.

Garry scribbled an informing message for the airport owner, detailing their purpose, and what they had experienced and the condition of the airport. Then he rejoined Don, the chocks were removed, and as he stepped away, with a wave, Don, alone, sent the Dart aloft.

Hardly waiting to see the fleet raft begin its trip toward the scene of their many mysteries, Garry hurried down to the wharf and water runway, down which the land-and-water types of craft were sent from the hangar: to one side was a landing stage for passengers from seaplanes, and at the end of that lay tied the “crash boat,” a swift, electrically propelled cruising launch kept always ready in case of any mishaps to seaplanes or other craft over the bay.

To clamber in, unleash the swift craft, and swing it out from the wharf with its speedy, quiet motor humming a low, soft drone, was the work of a moment for Garry, whose assignment in an emergency was at the speed control of the “crash boat.”

The prow of the speedy vessel turned North, angling across the inlet to skirt the point of land he must turn to get to the swampy channels beyond.

Garry knew the channels quite well, and, in the darkness, with only a dim gleam showing from his small forward light, a double, red-and-green cruising lantern, he was able to scan the starry sky and, as he coursed along the shore, passing the mouths of inviting channels, to discern, quite low, and inland, the flying lights of Don’s ship.

Their plan was simple.

Don, cruising, in the air, would discover if that lure called him, tempted him to set down—perhaps to some dreadful fate.

Garry, in the silent-motored, and fast little “crash” launch, would follow the shore to a channel known as Crab Channel. Down its somewhat deep and broad course he could turn inland, coming closest to the scene of their mission.

Then, hidden from inland eyes by tall grass, he could use a strong flashlamp to signal to Don, who would be circling wide. If Don saw the signal, and thus knew that Garry was ready, he would put out his flying lights. Then, dropping low, he would circle over the area Garry must reach.

With his own motive power so quiet, Garry could locate easily the sharp, intermittent periods of noise as Don alternately fed full-gun and gunned down. The noise, they knew, and Don’s low altitude, would fully occupy the attention of their quarry.

Don would hold his tight circle, climbing a trifle, gliding, keeping his motor alternately full-gun and still. Garry, creeping in through the most available channel offshoot, could locate the object of the ruse and then, surprising him, set off a self-igniting flare, attack, and at least hold the Demon, victim of the surprise, until Don could set down and help make his capture certain.

Everything went smoothly. Garry gave his signal. Don’s low flying lights winked to blackness.

Over the swamp, two hundred feet up, he cruised back toward some hidden adversary, menacing, terrible, watchful.

Swiftly, silently, Garry’s light motor impelled the “crash” launch up a channel which, with his alert ears guiding him, brought him closer and closer to the dark spot wherein, from the water level, he saw a weird sight.

Floating on a still, shallow pool, supported by its queerly designed pontoons, the helicopter was hardly visible in the shadowy eel grass: its horizontal blades, tilted by some device to a vertical line, made only a thin, invisible angle to the sky, although Garry, from his lower point of vantage, saw the outline against a starry background.

Intermittently, from the cockpit, and thus concealed and throwing its beam upward only, came the periodic flickers of a handkerchief-wrapped flash torch.

Its intermittent, dim glow illuminated the almost shapeless form and backward-thrown head of the Thing that never was, the Man Who Never Lived.

Tide-drifted, flare in hand, Garry floated toward the Demon’s Lair.