There was good reason for the fact that Tess and Dot were not soon missed. The older sisters had left the little ones playing near the tent when they strolled away themselves to see if any success was attending the efforts of the boys and Mr. Howbridge in their search for water.

The heat of the day was over. The breeze had sprung up and laved their faces delightfully as the girls strolled toward the hill on which the big palm tree grew.

The two older sisters found that the boys and their guardian had gone around the foot of the hill which occupied the middle of Palm Island, but they started to mount the slope of the smooth eminence.

"I wish we could see some boat and attract its attention," sighed Ruth, as they went on. "Then it wouldn't matter about the water supply or about repairing the engine of the Isobel."

"I guess we have been castaways long enough," agreed Agnes. "It would be awful if we had to stay here much longer. Think of our nice dresses there at the hotel all going to waste."

Ruth smiled indulgently. "We can wear them when we go back North."

"Oh, they'll be almost old by that time," declared the younger girl sadly. "And I did so want to wear 'em where Nalbro Hastings and those other girls could see that we weren't frumps, even if we did come from Milton."

"I never!" exclaimed Ruth, laughing. "You are the strangest girl, Aggie."

"Ought not to be strange to you, Ruthie. You've known me all my life,"

remarked the flyaway sister, smiling. "And I did want to sport my new frocks!"

"So you shall," said Ruth, comfortingly. "I don't think we shall have to remain on Palm Island much longer. Luke tells me he is sure that the engine will be all right soon. He knows a good deal about such things."

"Oh, Ruth!" exclaimed Agnes suddenly, "there's a boat coming to rescue us now!"

They were about half way up the slope of the hill. Agnes had turned to look back, and right over the lower trees and the rocky end of the island a craft of some kind was visible. Ruth, quite as excited as her sister, turned sharply to look in the direction Agnes pointed.

"From that way?" she murmured. "St. Sergius isn't over there, Aggie."

"I don't care. You can see the boat, can't you?" cried Agnes eagerly.

"Hurrah! I want to tell Neale. I saw the boat first."

"Wait!" commanded Ruth, seizing the excited girl's arm. "That boat is not coming this way, I am afraid."

"It's never got past the island without our seeing it!" wailed Agnes.

"Never!"

"I-don't-know--"

"I wish we had put up a flag-a signal of some kind," Agnes continued to complain. "Oh, Ruthie! If they have gone right by without seeing us! I would have sacrificed my sports skirt for a flag and worn-worn a gunny sack, if necessary! This is too mean."

"Wait, Aggie!" exclaimed Ruth, still staring at the boat Agnes had first spied. "There-there is something the matter with that boat. What propels it?"

"It is a motor-boat like ours, of course," rejoined Agnes quickly.

"It is not moving fast enough for that. And there is no sail. And I cannot see anything moving on that boat."

"For goodness' sake, Ruthie! Is it a boat sailing all by itself?" Agnes demanded.

"Exactly. That is what it is. The boat has broken away--"

"Well, now!" gasped Agnes. "Isn't that strange? And it's a motor-boat like the _Isobel_."

"Oh, Aggie!" cried Ruth, turning to her with a frightened face now.

"Aggie! It is our boat! It's broken away, somehow. We are now really cast away on this island. What will become of us?"

Agnes Kenway felt immense dismay at the possibility of the truth of her sister's statement. But Ruth was so utterly despairing that the younger girl felt she must comfort her.

"If it's the _Isobel_, we're lucky not to be in her," she said. "I guess we would have to wait for some other boat to come after us, anyway; so we are no worse off than we were before."

"How can you say that?" Ruth demanded. "Luke was sure he had almost got at the cause of the trouble with the mechanism."

"Well, let's not cry about it," begged Agnes. "Oh, don't, Ruth! If Tess and Dot see you in tears--"

Ruth dried her eyes suddenly. "I wonder where the children are?" she murmured. "I wonder if they have seen the boat drifting away?"

"And I don't believe Neale O'Neil knows about it. I am going to run and tell him," said Agnes, who always made Neale a partner in everything that happened to her.

She darted off excitedly. Ruth started back toward their camp. As she pushed through the shrubs, hastening her steps, she wondered where Tess and Dot were. By and by she began to call them by name; but she received no reply save the raucous cries of the water-fowl and the chattering of parakeets.

Ruth Kenway began to be alarmed in earnest.

CHAPTER XVIII

A NIGHT OF DESPAIR

Agnes Kenway was as light-footed as a deer. She ran as hard as she could around the slope of the hill on which the big palm grew, and thence down into the green wood. She shouted as she ran and soon heard Neale O'Neil reply.

"What's broken loose, Aggie?" demanded the boy, as soon as she came into view of the waterhunting party.

"That's exactly what has happened, Neale," she returned, in accents which a.s.sured both Neale and the others that she was quite in earnest.

"Something has broken away! The Isobel!"

Mr. Howbridge came running with Luke. The lawyer's face was white, for he had heard the girl's statement.

"You don't mean that the boat is gone?" he cried.

"So Ruthie says. She is sure," choked Agnes. "We saw it from up there on the hill."

Luke and Neale at once dashed away, climbing the hillside with great leaps. But Agnes remained with her guardian.

"We had just found a spring. A good one, too," murmured the troubled gentleman. "Well, perhaps that is a good thing. If the boat has really drifted away."

"Oh! It has! It has!" cried the girl. "Everything bad is happening to us. I wish we were at home at the Corner House again."

"Tut, tut! That is no way to talk," said Mr. Howbridge, and took her arm as they started in an easterly direction again.