It was after luncheon before the three friends got away from the Stone bungalow in the catboat.  Tom owned a catrigged boat himself on the Lumano river, and Helen and Ruth, of course, were not afraid to trust themselves to his management of the Jennie S.

The party was pretty well broken up that day, anyway.  Mercy and Miss Kate remained at home and the others found amusement in different directions.  Nobody asked to go in the Jennie S., for which Ruth was rather glad.

Mr. Hicks had gone over to Sokennet with the avowed intention of interviewing every soul in the town for news of Jack Crab.  Somebody, surely, must know where the assistant lighthouse keeper was, and the Westerner was not a man to be put off by any ordinary evasion.

“My Jane Ann may be hiding over thar amongst them fishermen,” he declared to Ruth before he went away.  “He couldn’t have sailed far with her that night, if he was back in ’twixt two and three hours.  No, sir-ree!”

And that was the thought in Ruth’s mind.  Unless Crab had sailed out and put Nita aboard a New York, or Boston, bound steamer, it seemed impossible that the girl could have gotten very far from Lighthouse Point.

“Shall we take one of the rowboats in tow, Ruth?” queried Tom, before they left the Stone dock.

“No, no!” returned the girl of the Red Mill, hastily.  “We couldn’t land on that island, anyway.”

“Only at low tide,” rejoined Tom.  “But it will be about low when we get outside the point.”

“You don’t really suspect that Crab and Nita are out there, Ruth?” whispered Helen, in her chum’s ear.

“It’s a crazy idea; isn’t it?” laughed Ruth.  Yet she was serious again in a moment.  “I thought, when Mother Purling spoke of his going there so much, that maybe he had a reason ­a particular reason.”

“Phineas told me that Jack Crab was the best pilot on this coast,” remarked Tom.  “He knows every channel, and shoal, and reef from Westhampton to Cape o’ Winds.  If there was a landing at Thimble Island, and any secret place upon it, Jack Crab would be likely to know of it.”

“Can you sail us around the Thimble?” asked Ruth.  “That’s all we want.”

“I asked Phin before we started.  The sea is clear for half a mile and more all around the Thimble.  We can circle it, all right, if the wind holds this way.”

“That’s all I expect you to do, Tommy,” responded Ruth, quickly.

But they all three eyed the conical-shaped rock very sharply as the Jennie S. drew nearer.  They ran between the lighthouse and the Thimble.  The tide, in falling, left the green and slime-covered ledges bare.

“A boat could get into bad quarters there, and easily enough,” said Tom, as they ran past.

But when he tacked and the catboat swung her head seaward, they began to observe the far side of the Thimble.  It was almost circular, and probably all of a thousand yards in circumference.  The waves now ran up the exposed ledges, hissing and gurgling among the cavities, and sometimes throwing up spume-like geysers between the boulders.

“A bad rock for any vessel to stub her toe against trying to make Sokennet Harbor,” quoth Tom Cameron.  “They say that the wreckers used to have a false beacon here in the old times.  They used to bring a sheep out here and tie a lantern to its neck.  Then, at low tide, they’d drive the poor sheep over the rocks and the bobbing up and down of the lantern would look like a riding light on some boat at anchor.  Then the lost vessel would dare run in for an anchorage, too, and she’d be wrecked.  Jack Crab’s grandfather was hanged for it.  So Phineas told me.”

“How awful!” gasped Helen.

But Ruth suddenly seized her hand, exclaiming:  “See there! what is it fluttering on the rock?  Look, Tom!”

At the moment the boy could not do so, as he had his hands full with the tiller and sheet, and his eyes were engaged as well.  When he turned to look again at the Thimble, what had startled Ruth had disappeared.

“There was something white fluttering against the rock.  It was down there, either below high-water mark, or just above.  I can’t imagine what it was.”

“A seabird, perhaps,” suggested Helen.

“Then where did it go to so suddenly?  I did not see it fly away,” Ruth returned.

The catboat sailed slowly past the seaward side of the Thimble.  There were fifty places in which a person might hide upon the rock ­plenty of broken boulders and cracks in the base of the conical eminence that formed the peculiarly shaped island.

The three watched the rugged shore very sharply as the catboat beat up the wind ­the girls especially giving the Thimble their attention.  A hundred pair of eyes might have watched them from the island, as far as they knew.  But certainly neither Ruth nor Helen saw anything to feed their suspicion.

“What shall we do now?” demanded Tom.  “Where do you girls want to go?”

“I don’t care,” Helen said.

“Seen all you want to of that deserted island, Ruthie?”

“Do you mind running back again, Tom?” Ruth asked.  “I haven’t any reason for asking it ­no good reason, I mean.”

“Pshaw! if we waited for a reason for everything we did, some things would never be done,” returned Tom, philosophically.

“There isn’t a thing there,” declared Helen.  “But I don’t care in the least where you sail us, Tom.”

“Only not to Davy Jones’ Locker, Tommy,” laughed Ruth.

“I’ll run out a way, and then come back with the wind and cross in front of the island again,” said Tom, and he performed this feat in a very seamanlike manner.

“I declare! there’s a landing we didn’t see sailing from the other direction,” cried Helen.  “See it ­between those two ledges?”

“A regular dock; but you couldn’t land there at high tide, or when there was any sea on,” returned her brother.

“That’s the place!” exclaimed Ruth.  “See that white thing fluttering again?  That’s no seagull.”

“Ruth is right,” gasped Helen.  “Oh, Tom!  There’s something fluttering there ­a handkerchief, is it?”

“Sing out! as loud as ever you can!” commanded the boy, eagerly.  “Hail the rock.”

They all three raised their voices.  There was no answer.  But Tom was pointing the boat’s nose directly for the opening between the sharp ledges.

“If there is nobody on the Thimble now, there has been somebody there recently,” he declared.  “I’m going to drop the sail and run in there.  Stand by with the oars to fend off, girls.  We don’t want to scratch the catboat more than we can help.”

His sister and Ruth sprang to obey him.  Each with an oar stood at either rail and the big sail came down on the run.  But the Jennie S. had headway sufficient to bring her straight into the opening between the ledges.

Tom ran forward, seized the rope in the bow, and leaped ashore, carrying the coil of the painter with him.  Helen and Ruth succeeded in stopping the boat’s headway with the oars, and the craft lay gently rocking in the natural dock, without having scraped her paint an atom.

“A fine landing!” exclaimed Tom, taking a turn or two with the rope about a knob of rock.

“Yes, indeed,” returned Ruth.  She gave a look around.  “My, what a lonely spot!”

“It is lonely,” the youth answered.  “Kind of a Robinson Crusoe place,” and he gave a short laugh.

“Listen!” cried Ruth, and held up her hand as a warning.

“What did you hear, Ruth?”

“I thought I heard somebody talking, or calling.”

“You did?” Tom listened intently.  “I don’t hear anything.”  He listened again.  “Yes, I do!  Where did it come from?”

“I think it came from yonder,” and the girl from the Red Mill pointed to a big, round rock ahead of them.

“Maybe it did, Ruth.  We’ll ­yes, you are right!” exclaimed the boy.

As he spoke there was a scraping sound ahead of them and suddenly a tousled black head popped, up over the top of the boulder from which fluttered the bit of white linen that had first attracted Ruth’s attention.

“Gracious goodness!” gasped Helen.

“It’s Nita!” cried Ruth.

“Oh, oh!” shrilled the lost girl, flying out of concealment and meeting Ruth as she leaped ashore.  “Is it really you?  Have you come for me?  I ­I thought I’d have to stay here alone forever.  I’d given up all hope of any boat seeing me, or my signal.  I ­I’m ’most dead of fear, Ruth Fielding!  Do, do take me back to land with you.”

The Western girl was clearly panic-stricken.  The boldness and independence she had formerly exhibited were entirely gone.  Being marooned on this barren islet had pretty well sapped the courage of Miss Jane Ann Hicks.