“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 glass 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 grass 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?

They gazed about them at the stretch of lone bay or inlet, the sparse scrub grass and vegetation fringing it on the shore side and wheeling sea-gulls swooping and soaring above the shoal waters.

Then Rob’s gaze rested carelessly on a closed and seemingly deserted bungalow, occupying the island above them.  As his eyes fell on it they suddenly became riveted and then grew wide with surprise.