"Say, Tubby, get out the lead line and let's see how much water we have," directed Rob as the color of the ocean began to change from dark blue to a sort of greenish tinge, lightening in spots, where the shoals were near to the surface, to a sandy yellow.

The stout lad took a position in the bow and swinging the lead about his head cast it suddenly ahead of the Flying Fish's bow.

"Slow down," ordered Rob, and Merritt cut down the motor to not more than two hundred revolutions a minute.

The lead line, tagged with different colored bits of flannel at each fathom length, sang through the stout lad's fingers.

"By-a-quarter-three," he called out the next instant.

This meant that three fathoms and a quarter or eighteen feet three inches of water was under the keel of the little craft.

"Nough fer a man-uv-war," grinned old Captain Hodgins.

Slowly the Flying Fish forged ahead till right under her bow lay a patch of the yellow water.

"By-a-half-two," came a sharp hail from the fat youth, who had once more heaved the lead.

"Cut her down some more," sharply ordered Rob, without turning his head, "we draw only three feet so I guess we'll do nicely for a while."

"Great hop-toads, there's regular shark's teeth ahead," commented Captain Hudgins, pointing to the still shallower water indicated by the lightening tint of the channel.

"By-one-by-a-quarter-one!" came sharply from Tubby, as the Flying Fish seemed hardly to crawl along the water.

"By-a-half!" came an instant later, meaning that only three feet of water lay right ahead.

"Stop her," roared out Rob.

But he was too late. Instantly, almost as Merritt's hand had flown to the lever, the nose of the Flying Fish poked into the sandbank and her motor with a gentle sigh came to a stop.

"Hard a-ground!" roared the captain, "too bad and with a fallin' tide, too."

"Full speed astern," came the next order.

The propeller churned up the water aft into a white turmoil. The Flying Fish trembled in her every timber, and began to slide slowly backward from the treacherous shoal.

"Safe, by the great horn spoon!" roared the captain, fetching Andy Bowles a slap on the back that almost toppled the small bugler into the water.

"For a time," said Rob quietly, "come ahead a bit, Merritt."

Slowly the little vessel slid ahead once more. Rob seemed fairly to feel his way through the narrow channel he had picked out and finally the Flying Fish, after as much coaxing as is usually bestowed on a balky horse, floated in the deep water beyond the sandy bar.

Eagerly the boys looked about them as they "opened up," as sailors call it, the narrow stretch of water known as the Upper Inlet. It did not take them long to spy the island with the tent on it in which the conversation between Jack and his cronies, and the mutineer to his plans, had taken place.

"There's their camp!" shouted Rob, eagerly sending the Flying Fish ahead at full speed, "now we'll find out something."

"And, maybe, use this." The captain, as he spoke, grimly produced his formidable weapon and flourished it about.

"No, none of that," sternly rejoined Rob, "the Boy Scouts can take care of those fellows--without using firearms."

"You bet," rejoined Merritt, grimly "muscling up," "we'll show 'em if it comes to a fight."

But bitter disappointment awaited the boys. As we know, the camp was deserted and no trace or clue of the whereabouts of its occupants was to be found. In the tent, however, lay a piece of blotting paper with ink-marks on it. It was the material with which Jack had dried his letter.

"Anybody got a mirror?" asked Rob. "This blotter may help some if we can read what's on it."

"I've got a pocket one," said Andy Bowles, who was somewhat particular about his person and always carried a small toilet case.

"That will do; let's have it."

Rob seized the bit of looking gla.s.s and held the blotter to it.

"Just as I thought," he exclaimed a minute later, with a cry of triumph. "It's Jack Curtiss' writing, though he has tried to disguise it, and they've got Joe hidden somewhere. Look here, they want $200 for his return."

"Yes, but what good does it do us to know that," objected Merritt, when the sensation this announcement caused had subsided. "They evidently had him here overnight and then deserted the camp for fear we'd pick up their trail. They've taken Joe with them."

"By the great sea-serpent, that's right," grunted the captain, "it's a blind trail, boys!"

CHAPTER XXI

SAVED BY "SMOKE MORSE"

Each member of the party regarded the other blankly.

The captain was right. The deserted camp was only a blind trail and they had all their work to do over again.

"The first people to communicate with are Joe's parents," mused Rob.

"That note will be delivered very shortly, as the longer they delay the more dangerous it will be for them."

"That's right," agreed Merritt, "Jack and his gang will not let the gra.s.s grow under their feet now that they know the chase must be on.

What can they have done with Joe?"

Rob had been looking about him with the instinct of the Boy Scout. He was anxious to ascertain if there were not something tangible, some clue on which they could base a search for the missing member of the Patrol. Suddenly something remarkable struck him about the tracks that lay about the tent.

They were all four those, of persons of larger growth than Joe Digby and mingling with them unmistakably was the broken-shoed track of Hank, the beach-comber.

"Boys," announced Rob suddenly, "Joe has not been here at all."

"Not been here at all," echoed Merritt, amazedly.

"I mean what I say. Look at these tracks. There is not a footmark here that could by any chance be his."

The others scrutinized the maze of foot-prints with the same care as had Rob and were forced to come to the same conclusion. There was no question about it--they would have to seek elsewhere for a trace of the lad.

But where?