“How did you ever guess the gem was in the gum?” Dick stared admiringly at Sandy, exultantly at the green light flashing from that hidden emerald as Sandy scraped aside the clinging substance from it.

“First the gum was in the amphibian,” Sandy said, trying to be as modest as the discovery would let him, “then it was gone. We thought we saw somebody in the hangar when first we went in—but he got away somehow. Then we saw the amphibian flying and it flashed over me that whoever we had seen before had been working on the amphibian and had chewed up all those pieces of gum—but I didn’t see why he had left it there. Then, when we found out that the man calling himself ‘Everdail’ didn’t look for or miss the gum, I guessed that he hadn’t been the gum chewer—but who had, then, I wondered. And why. It must have been for some reason, because if he had found the gum when he came to play ghost, keep everybody away from the estate by scaring them, and get the amphibian ready, he’d have throw any gum he found into the waste can.”
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“The gum was there for some reason,” agreed Dick. “This is one time when being suspicious has paid,” he added.

“Yes,” Sandy admitted. “When the life preserver was found and no gems were in the oilskin tied to it, and Dick showed me the gum, the reason for the big chunks of old gum came to me. The passenger had been getting it ready. He had to chew a great lot to get enough.”

“We mustn’t waste any more time,” cried Larry, eagerly. “There are twenty-nine more chunks in the seaplane. Let’s fly there, Jeff, and get it.”

“That-there is good sense.” Jeff started toward the flying field. “The fellow we didn’t find might come back for the emeralds.”

Going with them, to help out, Dick told Larry that he proposed to go at once to the various airports and flying fields, to learn, if he could, who had engaged the seaplane.

“The new Floyd Bennett field is the best chance,” argued Jeff. “They have got water and seaplane facilities there. It’s on Barren Island, and that’s where a man could have gone, in about the time between your seeing the ‘spook’ and the time the seaplane got where the yacht was.”
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“I’ll wait for the yacht,” Sandy said, accompanying them. “Mrs. Everdail will be glad to see what I discovered.”

That gave each of the members of the Sky Patrol something to do.

Dick had no difficulty in learning, when he got the executives of Bennett field interested that the seaplane was an old one belonging to a commercial flying firm operating from the airport.

“The pilot who handled the control job,” the field manager told him, “was a stunt man who has been hanging around since he stunted on our opening day. I’ve questioned some of the pilots for you, but no one seems to know who the pilot had with him. A stranger, one says.”

That brought Dick’s quest to a dead stop.

Sandy had even less success. Although in the short time since his disappearance the supposed impersonator of Mr. Everdail could not have gone far, he was not to be discovered by any search Sandy could make.

Farmhouses had no new “boarders.” The house on the estate, searched with youthful vim and alert thoroughness, revealed no observable hiding places. Sandy finally gave up.
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The arrival, anchoring and debarkation of its people by the yacht allowed him to meet and to reassure Mrs. Everdail and Captain Parks.

Besides these two he met the almost hysterical French maid, Mimi, also Mrs. Everdail’s companion and cousin, who had traveled with her, a quiet, competent nurse and attendant whose lack of funds compelled her to serve as a sort of trained nurse for the millionaire’s wife, who was of a very nervous, sickly type.

In spite of everybody’s relief when Sandy displayed the emerald, the elderly trained nurse and companion insisted that Mrs. Everdail must retire, rest and recover from her recent exciting experience.

Sandy, left alone, searched the hangar for an unseen exit, but found none.

Landing the amphibian, at almost the same spot they had set down before, Jeff looked around for the rubber boat they had left tied to a sunken snag.

“I guess Sandy’s ideas were right, after all,” decided Larry as he saw that the small water conveyance was not there. Sandy had claimed that if the missing seaplane passenger had hidden during the recent search of the seaplane, the boat would aid him to escape from the otherwise water-and-swamp-bound place.
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“If the rubber boat’s gone,” Jeff commented, “the twenty-nine other emeralds of the thirty on the necklace—they’re gone, too.”

“I’ll have to swim over again and see.” Larry stripped and made the short water journey.

“They’re still here,” he shouted across the channel.

Jeff, who had kept his engine idling, decided to risk a closer approach in the amphibian whose lower wingspan barely cleared the tops of grass clumps.

“I guess there aren’t any snags to rip the pontoons,” Larry assured him. To get closer would save Larry many trips to and fro in the water.

“Fine!” Larry commented as the amphibian, moving cautiously, came close enough for him to catch a rope and put a loop around the closest truss of the submerged seaplane. Thus he was able to pass the chunks of gum to Jeff, who had his clothes on and pockets for storage.

While the transfer was being made the amphibian’s engine died with unexpected suddenness.

“Golly-gracious!” Larry exclaimed, “I’ll bet she’s out of gas.”

“Can’t tell by the gauge.” Ruefully Jeff upbraided his stupidity in forgetting to see if they had to gas up before the take-off from the estate.
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“Now what’s to do?” he wondered.

Larry, too, saw a number of difficulties—perhaps more than did Jeff, because, from Larry’s point of view, due to Sandy’s suspicion of the superstitious pilot, Jeff must not go free with the gems in his pockets, nor did Larry dare be the one to go. If he did, Jeff might be playing a trick, let him get beyond chance of return in time, use some reserve gas and fly away.

“I can’t swim,” Jeff began, considering the ways of escape to some place where they could secure a supply boat with fuel.

“I wouldn’t chance swimming all the way down the swamps to the nearest village on shore,” Larry said quietly.

“This-here is a fix that is a fix,” morosely Jeff summed up the situation. “Here we are with a pocketful of emeralds—and no gas and no way to get to any—and if anybody knows the gems are in this gum—we’d be helpless if they wanted to take them.”

Larry did not answer.

He was mentally going over the seemingly unbreakable deadlock.

One thing that kept coming into his mind was the strange fact that if the disappearing passenger of the seaplane had taken the rubber boat he had not also taken the hidden jewels.
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“He must have known something about them—or guessed,” he reflected. “If they were put in the gum while they were flying—unless it was done while they were in the fog. But, even then, he knew all that excitement meant something. I don’t understand it—he did know, because he must have hired the pilot and the seaplane to............