As they were about to curl up and go to sleep they heard the sound of a seaplane droning overhead. It came over the island twice, and then went away.

And then, about an hour later, the girls heard the noise of the motor-boat! It grounded on the sand of the cove and the girls heard men's voices.

"Good gracious!" said Jill, sitting up in alarm. "What are they coming here at this time of night for? They will soon see the boys aren't here! Quick, Mary, get up. We'll slip out of the tent and go into the bracken. Maybe we can pretend we've been roaming over the island, and they'll think the boys are somewhere about too."

The girls left the tent and ran into the heather and bracken in the middle of the small island. The men left their boat on the beach and two of them came up to the tent.

They lifted the flap of the tent and flashed a torch inside. There was no one there, of course! One of the men called out loudly.

"Now, you children! Where are you?"

"Here!" answered Jill. She nudged Mary. "You shout too," she whispered. "Then I'll shout again, and they'll think we are all here."

"We're here!" yelled Mary valiantly, though her heart was beating hard.

"In the bracken!" shouted Jill.

"Come along down here," commanded the man. He was the one who could speak English.

"We shall have to go," said Jill. "Now don't you give the boys away, Mary. Pretend they are about somewhere."

The girls made their way to the men, who flashed a light on them.

"Where are the boys?" demanded the man.

"Haven't you seen them?" asked Jill. "They must be about somewhere. Maybe they are in the tent. Have you looked?"

"Yes," said the man. "Now look here—what do you mean by lighting this stove out here? Are you trying to signal to anyone?"

"Good gracious! Of course not!" said Jill. "We only made some hot cocoa, that's all. Look—there are our dirty cups."

She wished she had not said this when the man looked for the cups—for he saw at once that there were only two! He looked at Jill suspiciously.

"Why did the boys not have the cocoa?" he asked.

"They weren't here when we made it," said Jill. "Why don't you go and look for them?"

The man turned out the stove, and the light flickered and went out. "Now don't you dare to show a light at nights," he said. "If I think you are signalling to anyone you will be very sorry!"

"Who could we signal to?" asked Jill. "We don't even know where we are!"

The man took no notice of her. He stood and shouted into the night. "Boys! Come here at once!"

There was no answer, of course—there couldn't be, for the boys were miles away on the sea.

"To-morrow I will come to tell those boys that when I call, they must answer," said the man in an angry voice, "I am going now—but to-morrow I come again. You will tell the boys they must be here, by the tent."

Jill and Mary said nothing. They could not tell the boys—and they wondered what would happen when the men found that they were not on the island.

The men went off in their boat again. "What a pity we lighted that stove!" said Jill. "I suppose that seaplane saw it and reported it—and they thought we were signalling to someone. How clever they must think us! I only wish we could signal to someone!"

Neither of the girls could imagine what the men would do when they came to find the boys the next day, and saw that they were gone. They cuddled up together and tried to go to sleep. They awoke early and got themselves some breakfast. Then they sat waiting for the men.

There was nothing else to do—it was of no use trying to hide. They must just pretend that they did not know where the boys were.

The motor-boat did not arrive until mid-day. Then two men came up to the tent, and the one who could speak English looked at the two girls.

"What about those boys?" he said. "Why are they not here?"

"I don't know," said Jill, trying to speak bravely.

"Where are they?" asked the man angrily.

"I don't know," said Jill again, quite truthfully.

"You don't know! You don't know!" said the man in disgust. "It is time you did know. Are they on this island?"

"Why don't you look and see?" said Jill. "I am sure you will not believe what I say—so you had better look."

The men glared at the plucky little girl and then went to hunt over the island. They found no one, of course, and returned looking worried.

They spoke to one another in a language that the girls could not understand. Then they went to the ruined buildings and looked around carefully. It did not take them long to see that the boys had pulled the old shack to pieces!

"So!" said the first man. "The boys tried to make a boat!"

Jill and Mary shook their heads. They were really feeling very much alarmed.

"It is a raft they made then?" asked the man. "What! You will not tell me, you naughty little girls! Then I shall order out my seaplanes and they will find those bad boys, and bring them back again. And you will all be made prisoners on another island till we take you far away to our country where you will stay for a long time."

The girls began to cry—not because they were afraid for themselves but because they did not want the seaplanes to hunt for Andy and Tom.

The men spoke quickly to one another. It was plain that they wanted to get back to the third island and tell their chief what had happened.

"We shall come back for you to-morrow," said the first man. "And maybe by that time we shall have caught the two bad boys. They will be punished, you may be sure!"

They left in their motor-boat, leaving two miserable girls behind them. "Oh, I do hope they won't catch poor Andy and Tom," wept Mary. "It's too bad! Now they will hunt all over the sea till they find them. And they'll catch us to-morrow too, and take us all away."

"Well, they just won't take me away!" said Jill, drying her eyes fiercely. "I shall give them a good old hunt for me! I shall go to the second island and make them hunt all over the first one and not find mel That will give them a shock! I shall hide in the food-cave!"

"So will I!" said Mary, dabbing her eyes fiercely too. "We'll wait till the tide goes down and then we'll clamber over the rocks!"

So when the tide was low that day the two girls clambered hurriedly over the line of rocks that led from one island to the next, and came to the sandy beach. Not far off was the entrance to the cave that led up to the Round Cave.

"Nobody has seen us," said Mary, as they ran up to the cave. "We'll hide here and make the enemy think we've escaped from the island too! Perhaps they will be so busy looking for us that they will forget about the boys."

"I don't think they'll forget Andy and Tom," said Jill, making her way up the passage to the Round Cave. "I am sure that seaplanes are out looking for them already. I have heard three or four leaving the third island. Look, Mary—this chest is almost empty. Let's take out the tins and things that are left and get inside. We can shut the lid down on us if we hear anyone coming."

The girls got the chest ready, and then amused themselves by trying to find the funnel opening that led from the cave to the surface of the cliff above. But they could not find it.

"I wonder if it's night yet," said Mary, for it was impossible to tell in the dark cave. The girls had Andy's torch, for no daylight came into the cave at all. They crept to the shore-cave to see. Yes—it was twilight outside. Night would soon fall.

"I vote we make a nice soft bed in the sandy floor," said Jill. "We can cover ourselves with those empty sacks. And in the morning we'll peep out and see if we can see anything!"

So they made sandy beds and threw the sacks over themselves, they fell fast asleep and did not wake till morning.

And then, when they went to peep out of the shore-cave, they had a great surprise! Coming gracefully down to the smooth water was an enormous seaplane, droning like a great bumble-bee.