As the sun dipped towards, the mountains to the west and the boys did not return, Mr. Pauling became worried.

“I was a fool to permit them to go off alone,” he declared to Mr. Henderson. “Even with a compass they might go astray in the swamp. Boys are always careless and they do not realize the danger of getting lost.”

“Oh, I wouldn’t worry yet,” replied the other. “They have their radio sets along and would call us if they had any difficulties. Bancroft has been listening for the past hour and nothing’s come in.”

“Yes, I know,” rejoined Tom’s father, “but if they don’t turn up soon I shall start after them.”

Rawlins, who had returned from his scouting trip and had reported that he had been unsuccessful in seeing a sign of smoke across the bay, now approached.

“I hardly think they’re in trouble,” he said, “I I’d suggest calling them before starting a search, provided they don’t arrive. They can hear much farther than they can send and I don’t believe our messages could be heard by the gang in the sub. We’ve been several miles around the bay and know those rascals are not near.”

“Yes, we can do that,” agreed Mr. Pauling. “Even if they should hear, it is of little consequence in comparison with getting word to the boys. I’m about ready to abandon the attempt to locate the men anyway. Our information is too indefinite to rely upon.”

As time slipped by and still there was no sign of the missing boys and no word came by radio, Mr. Pauling became terribly worried and even Rawlins’ optimism became shaken.

Finally, as the afternoon shadows lengthened, Tom’s father could stand it no longer and he told Bancroft to call their names and see if he could get in touch with them. But when, after fifteen minutes, the operator reported that no response had been received Mr. Pauling grew frantic.

“Something’s happened,” he declared. “They’ve either gone too far to hear or to reply or they’ve been drowned or have met with some accident. We must set out on a search at once.”

Accordingly, the boat was manned, a radio set was placed in it and Mr. Pauling, Rawlins and Bancroft embarked, leaving Mr. Henderson, who was the only remaining member of the party who understood radio, in charge of the submarine. Sam also went along, for, as Rawlins explained, he had eyes like a cat and at Mr. Henderson’s suggestion Smernoff was included.

“You may hear those rascals talking,” he said, “and if you do you’ll need him.”

Rawlins remembered hearing the boys speak of the island they wished to explore and knew more or less the direction they had gone. It was no easy matter to find an island in the swamp largely by guesswork, but luck favored and just before dark they sighted the higher trees and firm land of the island where the boys had lunched. Calling frequently, both by voice and by radio, the searching party pulled around the island and came to the beach. Something white upon the sand attracted Rawlins’ attention and landing they found the paper wrappings of the boys’ lunch.

“They stopped here to eat,” announced the diver. “Now the question is in which direction they went. They might have gone up any one of these creeks or they might have started for the mainland. It’s all guesswork.”

It was now dusk and the swamp was black with impenetrable shadows, but as they circled around the swamp in vague hopes of finding some clue or of hearing the boys by the radio instruments, Sam’s sharp eyes caught sight of a bunch of water plants.

“Tha’ boat parsed by here, Chief,” he announced, pointing to the bruised and bent stems. “Ah’m sure of that, Chief.”

Rawlins examined the plants carefully. “Yes, either their boat or some other,” he agreed. “We’ll follow up this channel.”

By the time they reached the open lagoon it was pitch dark and their only hope lay in getting in touch with the boys by radio.

“If we don’t look out we’ll get lost ourselves,” announced Rawlins. “You watch the compass, Quartermaster, and keep track of our course and the bearings.”

“Aye, aye, Sir,” replied the old sailor, and once more the boat proceeded through the black swamp, Rawlins peering ahead and occasionally shouting, Bancroft constantly speaking into the instruments and listening at the receivers and Mr. Pauling, nearly mad with worry, fears and regrets.

For hour after hour they continued, following waterway after waterway, traversing lagoon after lagoon, forcing their way through the dense swamps to the mainland of the island and even emerging on the broad calm bay.

“If they’re lost and unable to get back they’ll probably camp,” said Rawlins. “They have matches and can make a fire. In fact they’ve sense enough to think of making a fire for a signal. I believe it will be a good plan to go ashore; I’ll ascend a hill, and Sam can climb a tree and look about. If there’s a fire anywhere in sight we should see it.”

All agreed this was a good plan and accordingly the boat was headed towards the nearest point and at last grated upon the rocks. With Sam, Rawlins pushed into the brush, stumbling over roots, bumping into trees in the darkness, barking shins and tearing clothes, but steadfastly clambering up the steep slope until they reached the summit. Selecting a tall palm, Sam proceeded to “walk” up the trunk in the native Indian fashion and soon reached the huge leafy top.

Straddling the base of an immense frond, he slowly and carefully swept the horizon with his eyes. From his lofty perch, nearly one hundred feet above the earth and fully two hundred feet above the water, the entire swamp, the numerous lagoons and even the broad bay lay spread before him like a map. Although the moon would not rise until midnight, yet the sky was bright with myriads of stars which cast a faint glow upon the water and served to distinguish; it from the darker masses of mangroves and land. At first he could see nothing that resembled the glow of a fire, but after several minutes his eyes detected a faint light among the trees several miles away and apparently on the mainland across the bay.

As he watched, the spot grew brighter, it took on a pinkish tint and seemed to spread, until at last, it was a distinct ruddy light which he knew beyond the shadow of a doubt was a fire. Carefully taking bearings by the stars and the dark masses of the swamp, he slid to the ground.

“Tha’s a fire yonder, Chief,” he announced. “Ah’ seed it plain an’ clear, an’ it’s just started, Chief. Ah seed it fla’in’ up an’ a-makin’ brighter all the time. Ah reckon tha’ young gentlemens ’s a-makin’ it fo’ a signal, Chief.”

“That’s blamed good news!” exclaimed Rawlins. “You say it’s over on the other side of the bay and you’ve got its bearings. All right, we’ll get over there, but how the deuce those kids got across the bay without knowing it, stumps me.”

Reaching the boat, Rawlins reported their success and with all possible speed the boat was pulled through the winding channels of the swamp in the direction Sam indicated. But it is one thing to take a sight and bearings from a tree top on a hillside and quite another matter to follow those bearings and directions through a mangrove swamp filled with twisting, devious channels. How Sam could manage to keep the general course at all was little short of marvelous, but as the boat turned bend after bend, doubled on its track, found its way blocked and made detours, the Bahaman never missed his general sense of direction, and at last the searching party emerged from the swamp and on the broad expanse of the bay.

Sam glanced about, squinted at the stars and indicated the course to follow. As they rowed swiftly across the bay towards the opposite shores, Rawlins spoke.

“Say!” he exclaimed. “It may not be the boys after all. I’ve been puzzling all along how they could get over there and I’m beginning to think it’s those chaps we’re after and not the boys.”

“Jove! you’re right,” cried Mr. Pauling, “and, good Lord! perhaps they’ve found the boys and taken them prisoners! If the boys used their radio to call us the others may have heard it and located them. What an addle-headed fool I’ve been to take such risks! No wonder we haven’t heard them or got them. Probably they’re helpless—bound and gagged and those devils are chuckling to themselves as they hear our calls and are luring us into a trap.”

“Well, if they’ve touched those kids I’ll say there’ll be some rough-house work when we step into that trap,” declared Rawlins, “and they’ll find they’ve bitten off a darned sight bigger hunk than they can swallow without choking. We’ve got arms, I slipped ’em in the boat, and we’re no crew of tenderfeet. Sam’s some little scrapper and the quartermaster was champion middle-weight of the Atlantic squadron, old Smernoff’s itching for a fight with those whiskered friends of his, and I guess you and Bancroft can take care of yourselves and I’m no quitter myself.”

“Yes, yes, Rawlins,” replied Mr. Pauling, “but you forget that if they have the boys they can protect themselves by threatening harm to Tom and Frank. They can make their own terms and they are ruthless beasts.”

“Well, Mr. Pauling, don’t let’s cross our rivers till we get to ’em,” said the diver. “We don’t know if the boys are prisoners yet. We’ll go easy and find out how the land lays first. Remember we can see their fire and what’s going on a long time before they can spot us. That’s the worst of a fire. The other fellow can see you, but you can’t see the other fellow.”

“Yes, but the great trouble is, if we call for the boys by radio we’ll warn our enemies instead,” Mr. Pauling reminded him.

“If they are prisoners it won’t be any use hollering for them,” replied Rawlins sagely. “I guess the best plan is just to lie low, keep quiet and sneak in. If the boys are alone and it’s their fire we’ll find them just as well without calling and if it’s the ‘reds’ fire and the boys are not there we’ll spring a surprise.”

A few minutes later the boat had gained the shelter of the trees beyond the bay and, still guided by Sam’s almost uncanny instinct or skill, they pushed into the nearest channel among the mangroves. On this side of the bay, however, there was much more open water; the trees were more scattered, and, instead of being made up of innumerable creeks flowing through dense masses of mangroves, the swamp consisted of large lake-like expanses dotted and interrupted by narrow belts and isolated clumps of trees.

They had proceeded for an hour or more and felt that they must be approaching the spot where Sam had seen the fire when they noticed that the darkness was less dense, that there was a subdued light upon the water, and that the clumps of trees were sharper and clearer.

“Hanged if the moon isn’t rising!” exclaimed Rawlins. “Crickey, it must be near midnight.”

Mr. Pauling looked at his watch. “It’s after eleven,” he announced. “We’ve been searching for five hours.”

“I’ll say those kids are some little travelers!” declared Rawlins. “They must have thought they were rowing for a bet to get clean over here.”

“Ah 'spec’ tha’ tide made to help them, Chief,” remarked Sam. “It makes right strong an’ po’ful up these creeks.”

“Yep, that must have been it,” agreed Rawlins. “Hadn’t thought of it before, I’ll bet they got caught in a strong current and couldn’t pull against it. Hello! What the——”

Instantly the men stopped rowing. From far away, as if from the air itself, came a low throbbing vibration, a sound felt rather than heard, and those in the boat stared at one another questioningly.

“Thunder!” suggested Mr. Pauling, in a low tone.

Rawlins shook his head. “Nix,” he replied crisply. “Thunder doesn’t keep up like that and it doesn’t throb that way. Sounds to me more like a ship’s screw half out of water.”

“Some bird then,” suggested Mr. Pauling. “Bittern or owl, perhaps.”

“I’ll say it’s some bird—if ’tis a bird!” exclaimed Rawlins. “What is it, Sam?”

The quartermaster spat into the water and before the Bahaman could reply he remarked: “’Course 'taint possible, Sir; but if I was a-hearin’ o’ that 'ere soun’ an’ was in the South Seas 'stead o’ here in the West Injies—I’d say as how ’twas a tom-tom, Sir—you knows what I means, Sir—savage drum such as they uses for a-havin’ of a cannibal feast, Sir.”

“Well we’re not in the South Seas,” returned Rawlins, “and there aren’t any cannibals here. Say, what the devil’s the matter with you, Sam?”

It was no wonder Rawlins asked. The Bahaman was staring open-mouthed across the water, his eyes rolling, his face drawn and awful fear depicted upon his black features.

“Here, wake up! Seen a ghost?” cried Rawlins, shaking the negro roughly. Sam’s jaws came together, he licked his dry lips and in terror-striken, shaking tones murmured, “Voodoo!”

Something in his tones, in the way he pronounced the one word, sent shivers down his hearers’ backs.

“Voodoo?” repeated Rawlins, recovering himself. “What in thunder are you talking about?”

“Ah knows it!” replied the negro, in a hoarse whisper. “Tha’s the devil dance! Yaas, Sir, tha’s Voodoo goin’ on!”

“Well, I’ll be sunk!” ejaculated the diver. “A Voodoo dance! By glory! I didn’t think they had ’em over here. I’ve heard of 'em in Martinique and Haiti, but I never took much stock in the yarns. Are you sure, Sam?”

The cowering negro had sunk to his knees in the boat. All the long-dormant superstition of his race, the soul-racking fear of the occult and supernatural which was the heritage of his African ancestors had been stirred into being by the throbbing pulsations borne through the night, and he was an abject, terror-stricken creature.

Rawlins jerked him to athwart. “Brace up, you fool nigger!” he commanded. “No one’s hurting you yet! You’re a blamed coward, Sam! What if ’tis Voodoo? What in thunder are you scared of?”

Slowly the negro came back to his senses; shaking like a leaf, sickly ashen with fright, he steadied himself. “Ah aint 'fraid,” he stuttered, his tones belying his words. “Ah was jus’ flustrated, Chief. But Ah don’t mek to meddle with Voodoo, Chief. Better go back, Chief.”

“You bet your boots we’ll go back—not!” declared Rawlins. “I’d like right well to see a Voodoo as you call it. And if there’s any folks around here—black or white, tame or savage, we’re out to find ’em and have a pow-wow with ’em. Maybe the boys saw their fire and made for it, and maybe the fire’s nothing to do with the tom-tom, and more likely than all it’s not a devil dance at all but just those blamed Bolsheviks having a vodka spree all on their own—celebrating the boys’ capture or something. Come on, men, let’s get a move on.”

“Perhaps we’d better try to call the boys,” suggested Mr. Pauling. “Your hint that they may have seen the fire, or that they may have heard the drum is reasonable, but they are cautious and might be near, hesitating to approach the fire or the sound. The noise of that drum—supposing it should be the ‘reds’ and not from a negro dance—would prevent others from hearing us.”

“Sure, that’s a good idea,” agreed Rawlins. “Maybe they’re near, right now.”

As Rawlins spoke, Bancroft was adjusting his instruments and the next instant gave an exultant cry.

“I hear ’em!” he announced.

Then: “Tom! Frank!” he called into the microphone. “Can you hear me? It’s Bancroft! We’re near! We can hear a drum and are making for a fire! Where are you? Can you see the fire or hear the noise?”

Faint and thin, but clearly distinguishable, now the throbbing rumble of the drum had ceased, Bancroft heard Tom’s voice.

“We hear!” it said. “Come quick! We don’t know where we are, but we’re here by the fire—we’re prisoners—a lot of savages have us!”

Bancroft, in a strained voice, repeated the words.

“Good Lord!” cried Mr. Pauling, “they’re captives of those crazy devil-worshipers.”

“Attaboy!” yelled Rawlins. “Lift her, boys! Pull for your lives!”