The next few days were exciting ones for the Overall Boys.

Joe said he knew that he was dreaming, and his dreams were all about castles and kings and queens and strange languages.

Jack had to tell him very often that he was sailing up the beautiful river Rhine toward Switzerland, that the castles and the kings and the queens and the strange languages were really true.

"I know that the castles are really here," said Joe, "for I am counting them. Look at that great fort on the hill!"

"Yes," said Jack, "the Captain says if we were their enemies, the soldiers in that fort would not let our boat pass up the river."

"Well, I am glad we are not their enemies," said Joe. "I don't like the looks of the big guns peeping through those holes in the fort walls. I like the old castles better."

And so the Overall Boys sailed by castles and still more castles, which were built high on the banks above the river. Most of them were very old, so old they were falling to pieces.

Lower down on the river banks there were large vineyards, where the finest grapes were growing.

Their father told the boys strange stories about the people who once lived in these old castles. He told them about a beautiful sea maiden who used to sit on a high rock above the river combing her long, golden hair and singing sweet songs. He told how brave young men sailed their boats into the dangerous waters to listen to her songs, and were drowned.

Fortunately the maiden did not sing while the Overall Boys were passing her rock, so they went safely on their journey.

A little later Jack cried, "Come, Joe, the Captain is going to tell us a story."

"Is he going to tell it in some dreadful, strange language?" asked Joe.

"No, sir!" said Jack. "This Captain knows how to speak English."

"Hello!" called the Captain. "Do you boys like mice? Both of you do! Well, that is brave. I am going to tell you about a man who did not like mice.

"Do you see that large, round tower just ahead of us? It is built on a rock in the middle of the river. It is called the Mouse Tower. This is the reason why.

"Once upon a time—I cannot tell you just how long ago, but once upon a time—there lived a rich Bishop. He lived in a great castle up there on the river bank. He had fine farms, and he made much money. He filled many barns with his grain, and he kept his gold in strong boxes.

"A great many poor people lived near the rich Bishop. He should have taught them how to work and how to pray, but he did not. He did not even give them grain when they needed it, or gold that they might buy bread.

"One year when the people were very hungry, they begged the Bishop so hard for bread that he could not sleep. He said they were like a pack of hungry mice.

"At last the Bishop told the beggars to go to an empty barn near by, and he would soon satisfy their wants. So the people hurried into the barn, and waited for the Bishop to come. He came, but he did not bring them food or gold.

"Oh, no! The selfish Bishop told his servants to set fire to the old barn, and the poor people who were inside soon stopped crying for food.

"That night while the Bishop was asleep in his castle, he dreamed a strange dream. He dreamed that some hungry mice were eating a fine picture of himself which hung on his bedroom wall. He watched them until they had torn it all to pieces.

"Just then a servant ran into his room and wakened him.

"'O Bishop Hatto! Bishop Hatto!' cried the servant. 'The mice are coming. They are coming out of the hot ashes of the old barn which we burned last night. They have followed me up to your castle. You must run for your life.'

"So the Bishop jumped on his horse and rode down the hill as fast as he could ride, and the mice ran after him. When he came to the river the mice were almost upon him.

"The Bishop left his horse and jumped into a small boat. He rowed very hard until he came to that stone tower in the middle of the river.

"'Now,' said he, 'I am safely away from those miserable mice.'

"But he was not safely away from them, for the mice could swim.

"The Bishop shut himself into the tower and closed the doors and windows. But the mice could gnaw. They ran up the stone walls and gnawed through the wooden doors. Then they ran down the doors on the inside and found the wicked Bishop.

"How the Bishop wished that he had been kind to the poor, starving people. How he wished that he had given them food and gold when they needed it so much. Now it was too late. The hungry people had sent their spirits back in these hungry mice to punish him as he had punished them.

"And so the old stone tower has been called the Mouse Tower, or Bishop Hatto's Tower, ever since. Now, what do you think of that for a story?" asked the Captain.

"I tell you, I hope I never shall be such a mean old Bishop as he was!" said Joe.

"And I am glad he is not living now!" said Jack.

Soon the Overall Boys had sailed as far up the beautiful river Rhine as their big boat would take them. They had seen so many old castles, and they had heard so many strange stories about them, the boys felt as if they had just passed through a really, truly Fairyland—and perhaps they had.