st 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 sai