Tom soon found foothold on the rocks under the water. He felt better at once. He and Andy held hands iSarf together made their way very cautiously over tins i sunken rocks, bruising their poor feet, but getting gradually nearer to the shore. And at last they felt the rocks stop, and there was sand beneath their feet! Good,

"Golly! I didn't enjoy that very much," said Tom. "Sorry I was so feeble, Andy."

"It's all right," said Andy. "You did your best. We're all right now."

But in his own mind Andy didn't think they were at all all right! How in the world was he going to get Tom over that stretch of water back to the second island gain? He would never, never do it! Andy was very worried indeed.

But he didn't show it. He grinned at Tom, his blue eyes shining in his wet brown face. "We're here at last!" he said. "And maybe we shall get a few surprises!"

They lay on the sandy shore in the sun for a while, drying themselves. Tom felt very much better alter a meal out of the oilskin packet. He almost felt as if he could swim back home again! It was wonderful what food did to Tom.

"I feel a new man now," he said, leaping to his feet. "Come on, Andy, old chap. Let's go up to the cliff-top and go across to the other side of this island, to see if we can spy anything."

Andy got up too. The two boys climbed up the rough cliff and sat on the top to get back their breath. The island seemed to be about the same as the other two—covered with heather, bracken and grass, and with white gulls soaring over it.

They crossed the narrow width of the island and at last came to the cliff on the other side.

"Wriggle along on the ground now, just in case there's anyone about," said Andy. So both boys wriggled along on their fronts, and came at last to a lace where they could see down to the water far below.

And what they saw there filled them with such astonishment and alarm that for at least five minutes neither boy could say a word!

Chapter 11

The Secret of the Islands

The sight that the two boys looked down upon was hardly to be believed. There was a very fine natural harbour of extremely deep water on the north-eastern ide of the third island—and lying in this water were at least seven or eight submarines!

Submarines! A submarine base in those deserted islands! No wonder so many of our ships had been sent to the bottom in the waters around these islands!

"It's a real nest of submarines," whispered Andy at last. "Enemy submarines I I can't believe it. My word, Tom, we've stumbled on an amazing secret."

The boys lay looking down on the water. Some of the submarines lay like great grey crocodiles, humped out of the water. One or two were moving out of the harbour, their periscopes showing. It was a curiously silent place, considering that so many of these underwater ships were there. There was no noise of shouting—no noise of machinery—just a dull throbbing every now and again.

"They get fuel and food here," whispered Andy. They are the small submarines—this harbour can easily take a dozen or more. It's a perfect place for submarines. Do you see how they haven't built any jetties or piers—not a thing that anyone could see, if one of our own planes came over? All they would have to do then would be to sink under the water—and then there would be nothing to see. They store everything in the caves—golly, it's amazing."

For a very long time the two boys lay watching the Strange sight below. Two submarines slipped silently out of the harbour entrance—a way between two reefs of high rocks. A third submarine came in, and lay peacefully with the others, the men coming out on the deck and looking around.

At first Tom had been so full of surprise and alarm, go swept with excitement, that he could think of nothing but the sight of the queer vessels. Then another thought came into his head and he turned to Andy.

"Andy," he said. "We've got to get home and tell what we've seen."

"I know," said Andy. "I'm thinking that too, Tom. And we've got to get the girls off these islands. We are all in danger. If the enemy knew we were spying on them like this I don't know what would happen to us."

"I don't care how much danger we're in," said Tom, and he didn't. "All I know is that we've got to go and tell our people at home about this submarine base. It's got to be cleared away. Andy, it's serious."

Andy nodded. Both boys seemed to become men at that moment. They looked gravely into each other's eyes and what they saw there pleased them both. Each boy knew that the other would do his best and even more than his best.

"Do you think we shall be believed if we go home with a story like this?" said Tom. "Grown-ups have some funny ideas sometimes. They might think we had made it all up—or been mistaken."

"We'll get your camera and take a few photographs," said Andy. "Nobody can disbelieve photographs. And another thing we must do is to try to do something with our boat. We must get it off the rocks somehow and try to patch it up. It's our only way of getting back home."

They watched the harbour for a little while longer, and then wriggled along the top of the cliff till they came to some bushes. They went down by these and ran along till they came to the end of the harbour. Beyond lay a cove, and in it, drawn up to the sand, were a number of small boats. No one seemed to be about.

The sight of the little boats excited Andy. If only he could get hold of one! Then he and Tom could row round the third island, and get back to the second one safely. Andy knew perfectly well that Tom could not swim back—and he did not mean to leave the boy alone on this submarine island.

"Tom," he said, "see those boats? Well, what about waiting til night-time—and then stealing down to the cove and taking a boat? We could easily row it back to the second island. It would save us having to swim—and we might even fill it with food and water and try our luck at going home. I could fix up the sail somehow."

"Good idea, Andy," said Tom, his face glowing with excitement. "But I say! Won't the girls be awfully worried if we don't swim back before low tide tonight?"

"We'll go to the cliff on the other side of this island and wave to them," said Andy. "They've got the field-glasses and will see us quite clearly. We'll point and wave and nod and try to show them that our plans are altered, but that we're all light"

"Good," said Tom, "Let's go now. I feel so awfully excited that I really must do something!"

The boys went to the other side of the island. After a while the girls appeared and waved to them. Jill put the glasses to her eyes.

The boys seem frightfully pleased and excited about something!" she said. "They are waving and pointing and nodding like anything. They seem to want us to understand something."

"Well, it-can only be that they have found something exciting and are going to do something about it," said Mary, taking the glasses from Jill and looking through them. "Yes—Tom's like a mad thing. Well, we shall know when they come back to-night. I only hope Tom will be able to swim back all right. I was really afraid he'd drown this morning."

The boys disappeared after a time. They sat down in a little sunny hollow and finished the rest of the food. Andy found a stream of water and the boys drank from it. Then they sat talking quietly, waiting for the night to come.

At last it came. The moon was behind the clouds, and gave only a pate light now and again. The boys, slipped quietly to the top of the cliff that overlooked the small cove next to the harbour. They had already planned the easiest way down. Andy went first. He climbed like a cat. Tom followed him, trying not to send any stones clattering down the cliff.

They came to the shore. It was sandy and their feet made no noise. The boys stayed in the shadow of the cliffs for a few minutes, listening. They could hear no noise at all, except the small sound of little waves breaking on the sand. The boats were not far off, upturned in a row. No one was guarding them. Indeed, why should anyone? No one had ever set foot on the islands since the farm-folk had gone—save for the crews of enemy seaplanes and submarines.