They all rushed into Jack’s bedroom at the top of the tower - but at the first look round Peggy gave a cry. “What sillies we are! There’s no fireplace here!”

“Goodness - of course not,” said Jack in dismay. “I’d completely forgotten that. But the map quite clearly shows that the passage starts somewhere in the chimney.”

“Our room below has a big stone fireplace!” cried Nora. “It must be there that the passage starts. Hurry!”

Down they tore to Nora’s room, where there was certainly a big, old-fashioned stone fireplace. Jack looked up it.

“Get me a stool or something,” he said. “I can stand on that and grope about.”

So, with the girls jigging impatiently about below, Jack stood on a stool and groped about in the dirty old chimney. At one side he felt what seemed to him to be narrow steps cut in the chimney. He told Miss Dimmy, looking down at her as black as a little sweep!

“Yes, that’s right, there would be steps there,” said Dimmy. “In the olden days small boys were sent up to sweep these big chimneys and sometimes steps were cut to help them. Can you get up them, Jack?”

Jack thought he could. So up he went, choking over the years-old soot. The steps were very small, and came unexpectedly to a little opening off the chimney itself. Jack was sure that the door to the hidden passage was somewhere in that opening!

The stones and bricks were intermixed there and were rough to his hand. He pulled and pushed at each one, hoping it would swing round and show him an opening beyond. But not until he suddenly slipped and bumped against a certain stone did anything move at all!

His shoulder fell against a stone that stood out from the rest. It gave under his weight, and seemed to swing round, giving a click as it did so. Jack quickly shone his torch on to it, and saw a small hole appearing in the wall of the chimney. He put his hand into the hole and felt an iron ring.

“I’ve found the entrance! I’ve found it!” he yelled down the chimney. He pulled hard at the iron ring, and felt the stone to which it was fastened move a little; but no matter how hard Jack pulled he could not make the stone move any farther.

He climbed down the chimney, and the girls cried out in horror when they saw his black face and hands. He grinned at them, and his teeth shone white in his mouth.

“Dimmy, we’ll have to get George to help us,” he said. “I think the entrance-stone is stiff with the years that have gone by since it was last used. If we got George to bring a thick rope and fasten it to the iron ring I’ve found up there, we could swing the stone round all right and see the entrance to the passage. The stone has moved just a little - I can see the crack with my torch where it should come away from its place.”

“George is working in the garden this afternoon,” said Dimmy joyfully. “We can get him easily. No, Jack, no, don’t you go and get him - you look so awful!”

But Jack was gone. He sped down the staircase and out into the garden. George was busy digging up potatoes. Jack burst on him, crying, “George, George, come quickly!”

George looked up in surprise, and saw a black, grinning creature running towards him. He got a tremendous shock and dropped his spade. It took him quite a minute before he would believe that the black creature was his friend Jack!

Talking eagerly and telling George things that astonished the farm-lad greatly, Jack led him up the stone staircase to the girls’ bedroom.

“Has he brought a rope?” cried Nora.

George nearly always had a rope tied two or three times round his waist. He gaped at the two girls and Miss Dimmy, and then said, “Where’s Mike?”

“You haven’t been listening!” said Jack impatiently. “I was telling you all the way up.”

“Let me tell him,” said Dimmy, seeing that George really was thinking that everyone was quite mad. So she told him the whole story as shortly as possible. George nodded his head solemnly every now and again. He didn’t really seem astonished now that he knew everything, but his eyes gleamed when he heard that Dimmy wanted him to go up the chimney and tie his rope to the iron ring.

“I’d like to get Mike back all right,” said George, undoing the rope round his middle. It proved to be very long and very strong. He disappeared into the chimney with Jack’s torch. Jack tried to climb up after him, he was so impatient, but came down at once, his eyes and mouth full of soot kicked down by George’s enormous boots.

George found the iron ring in the little opening and knotted his rope in it. The end fell down the chimney to the hearth like a brown snake. George jumped down.

“Now we’ll all pull,” he said, with his slow, wide smile. So they all pulled - and the rope gave a little as the big stone above swung round and back, leaving just enough room for anyone to squeeze through.

Jack climbed up the chimney again and gave a shout as he saw the dark opening. “Oh, the secret passage is here all right! Come on, all of you!”

Poor Dimmy! She was really horrified at seeing everyone go up that dirty, sooty old chimney and getting as black as negroes - but even she went up too, just to see what kind of a secret passage it could be!

George had squeezed through the opening that was made when one big stone had swung out of its place. It had been cunningly built on a kind of swivel set in the next stone, and when weight was put on to the iron ring the stone swung round.

A very narrow way led round the back of the chimney - so narrow that George had to walk sideways to make himself small enough. Then he came to an iron ladder set at his feet, disappearing down into the darkness. He called back to the children.

“There’s a ladder here, going downwards. I reckon there’s an outer wall and an inner wall to part of this tower, and that’s where the passage is! The rest of the tower wall is solid.”

Down the narrow iron ladder they all went. They had to hold their torches in their teeth, for they needed both their hands. Dimmy had no torch, so she stood at the top of the ladder, waiting for them all to return.

The iron ladder went right down inside the wall and ended below the tower itself. A small room was at the foot of the ladder, and in it the children saw two old tops, a wooden hand-carved toy boat and some old, mildewed books.

“This must have been Dimmy’s grandfather’s hidey-hole when he was a boy,” said Jack. “Look at his toys!”

From this small underground room, smelling so musty and queer, a narrow passage led up the cliff.

“This passage can’t be so very far underground,” said George, leading the way. “Hallo! Look there! Surely that is daylight?”

It was! A bright circle of daylight shone not far above their heads.

“I guess a rabbit has made its burrow above us,” said Jack, with a laugh. “He must have burrowed from the surface down to this passage. What a shock for him when he fell through!”

“Well, the bunny has let some fresh air into this place, at any rate,” said George. “Perhaps that is what has kept it fresh enough to breathe in.”

They went along the passage, and then came to a stop. “What’s up, George? Why have you stopped?” asked Jack.

“Because the passage has fallen in here,” said George. “We’ll have to get spades and dig it free again. The roof has fallen in, and we can’t get any farther. We’ll come back and dig it out. I reckon the passage goes on to the tower of the Old House, and then we’ll find an iron ladder going up inside the walls just as we found at Peep-Hole.”

The children squeezed back through the passage and went up the iron ladder to the chimney. Dimmy had got down again and was waiting for them in the girls’ room, having washed herself clean.

They told her excitedly what they had found. Jack ran down to the shed to get spades, and to find some biscuits for himself, for he had had no dinner.

“We shall be able to rescue Mike and Paul very soon now,” said Peggy hopefully.

“Better clear the passage now and try to get to the boys to-night,” said George thoughtfully. “You see, if we can rescue them at night there’s not so much fear of us being heard, and we can get a good few hours’ start of the folk at the Old House.”

“Right, George,” said Dimmy, who was just as excited as the children.

George and Jack went to clear the passage ready for the night’s adventure. The girls went to wash themselves, and to pore once more over the exciting diary that had told them just what they wanted to know.

In an hour’s time Jack and George came back, hot, dusty, sooty, and thirsty. Dimmy made them have a bath, and put on clean clothes - though George looked very comical in Mike’s shorts and jersey! Then they all sat down to a good tea, which they really felt they had earned.

“This is getting more and more exciting!” said Peggy, spreading her bread and butter with Dimmy’s homemade shrimp paste. “I feel as if I’m bursting with excitement. If only old Mike knew what we were doing!”

“He’ll know soon enough,” said Jack, with his mouth full.

“I reckon the queer folk up at the Old House will be pretty furious when they find Mike and the prince gone,” said George rather solemnly. “I think you’d better all get away from here with Paul, whilst Miss Dimity and I tell the police and find out a bit more about this prince of yours.”

“Get away from here?” said Jack. “But where could we go that was safe?”

No sooner had he said it than he and the girls had the most marvellous idea in the world.

“Our secret island! We’d be safe there! It’s not far from here!” yelled Jack.

“The secret island!” cried Peggy and Nora.

“What’s that?” asked George in astonishment.

“It’s on Lake Wildwater, about forty miles from here,” said Jack. “We lived on our secret island on the lake when we ran away once - it would be a wonderful place for the prince till he’s safe from his enemies.”

“Good idea!” said George. “I’ll take you round the coast in my boat to Longrigg, where I’ve a brother who has a car. He can drive you to Wildwater - and you can do the rest!”

“Won’t Mike be pleased, won’t Mike be pleased!” shouted Nora. “Oh, I do feel so happy!” And she danced poor Dimmy round and round the room till Dimmy had to beg for mercy!