They had brought their lunch with them, so they would not have to go back to the camp when noon came, and, finding a pleasant place on the beach, near a little spring of water, they sat down to rest.

Flossie and Freddie, as often happened, finished long before the others did, and soon they strolled off, hand in hand, down the sands.

"Where are you going, children?" called Mrs. Bobbsey to them.

"Oh, just for a walk," Freddie answered.

"An' maybe we'll see Jack," added Flossie.

"I only wish they would, but it is too much to hope for," said Cousin Jasper, and he looked worried.

Bert, Nan and the others stayed for some little time after lunch, sitting in the shade on the beach, and talking. They were just about to get up and once more start the search; when Flossie and Freddie came running back. One look at their faces told their mother that something had happened.

"What is it, children?" she asked.

"We--we found a big, black cave!" answered Freddie, somewhat out of breath.

"An'--an' they's a--a _giant_ in it!" added Flossie, who was also breathing hard.

"A cave!" cried Mr. Bobbsey.

"What do you mean by a giant in it?" asked Cousin Jasper.

"Well, when you see a big black hole in the side of a hill, isn't that a cave?" asked Freddie.

"It surely is," said his father.

"An' when you hear somebody making a big noise like 'Boo-oo-oo-oo! Boo!'

maybe that's a giant, like it is in the story," said Flossie.

"Oh, I guess perhaps you heard the wind moaning in a cave," said Captain Crane.

"No, there wasn't any wind blowing," Freddie said. And, surely enough, there was not. The day was clear and calm.

"We heard the booing noise," Freddie said.

"Are you sure it wasn't a mooing noise, such as the cows make?" asked Nan.

"There aren't any cows on Orange Island; are there, Cousin Jasper?"

asked Bert.

"I think not. Tell me, children, just what you heard, and where it was,"

he said to Flossie and Freddie.

Then the little twins told of walking along the hill that led up from the beach and of seeing a big hole--a regular cave. They went in a little way and then they heard the strange, moaning sound.

Cousin Jasper seemed greatly excited.

"I believe there may be something there," he said. "We must go and look.

If they heard a noise in the cave, it may be that it was caused by some animal, or it may be that it was----"

"Jack!" exclaimed Bert. "Maybe it's Jack!"

"Maybe," said Cousin Jasper. "We'll go to look!"

Cousin Jasper and Mr. Bobbsey walked on ahead, with Flossie and Freddie to show where they had seen the big, black hole. It was not far away, but so hidden by bushes that it could have been seen only by accident, unless some one knew where it was.

Outside the entrance they all stopped.

"Listen!" said Flossie.

It was quiet for a moment, and then came a sound that surely was a groan, as if some one was in pain.

"Who's in there?" cried Cousin Jasper.

"I am," was the faint answer. "Oh, will you please come in and help me.

I fell and hurt my leg and I can't walk, and----"

"Are you Jack Nelson?" cried Cousin Jasper.

"Yes, that's my name. A friend and I were wrecked on this island, but I can't find him and----"

"But he's found you!" cried Mr. Dent. "Oh, Jack! I've found you! I've found you! I've come back to get you! Now you'll be all right!"

Into the cave rushed Cousin Jasper, followed by the others. Mr. Bobbsey and Captain Crane had pocket electric flashlights, and by these they could see some one lying on a pile of moss in one corner of the cavern.

It was a boy, and one look at him showed that he was ill. His face was flushed, as if from fever, and a piece of sail-cloth was tied around one leg. Near him, on the ground where he was lying, were some oranges, and a few pieces of very dry crackers, called "pilot biscuits" by the sailors.

"Oh, Jack, what has happened to you? Are you hurt, and have you been in this cave all the while?" asked Mr. Dent.

"No, not all the while, though I've been in here now for nearly a week, I guess, ever since I hurt my leg. I can crawl about a little but I can't climb up and down the hill, so I got in here to stay out of the storms, and I thought no one would ever come to me."

"You poor boy!" softly said Mrs. Bobbsey. "Don't talk any more now. Wait until you feel better and then you can tell us all about it. Poor boy!"

"Are you hungry?" asked Freddie; for that, to him, seemed about the worst thing that could happen.

"No, not so very," answered Jack. "When I found I couldn't get around any more, or not so well, on my sore leg, I crawled to the trees and got some oranges. I had a box of the biscuit and some other things that washed ash.o.r.e from the wreck after you went away," he said to Cousin Jasper.

"Well, tell us about it later," said Mr. Bobbsey. "Now we are going to take care of you."

They made a sort of little bed on poles, with pieces of the sail-cloth, and the men carried Jack to the camp. There Captain Crane, who knew something about doctoring, bound up his leg, and when the lost boy had been given some hot soup, and put in a comfortable bed, he felt much better.

A little later he told what had happened to him.

"After you became so sick," said Jack to Cousin Jasper, the others listening to the story, "I walked to the other end of the island to see if I could not see, from there, some ship I could signal to come and get us. I was so tired I must have fallen asleep when I sat down to rest, and when I woke up, and went back to where you had been, Mr. Dent, you weren't there. I didn't know what had happened to you and I couldn't find you."

"Men came in a boat and took me away," said Cousin Jasper, "though I didn't know it at the time. When I found myself in the hospital I wondered where you were, but they all thought I was out of my head when I wanted them to come to the island and rescue you. So I had to send for Mr. Bobbsey to come."

"And we found the cave, didn't we?" cried Freddie.