The others stared at the rope. Mike caught hold of it.

It hung down from a black hole at the top of the rocky wall, and as he pulled it, it held firm.

“Yes, that’s what it is!” said Mike. “It’s fastened to something overhead, and is meant to help anyone using this cave. I’ll go up first with the rope’s help, and you others can follow.”

It was easy to get up the slippery, rocky steps with the rope to help them. Mike swung himself through the dark opening at the top of the sloping wall. He shone his torch around.

He was in another cave, but much smaller. A few boxes and barrels lay around empty and half broken.

Mike called down excitedly. “This has been used by smugglers in the olden days! There are still the old boxes here that must have brought the brandy and silks and things that the smugglers hid. Come along, you others!”

One by one they scrambled up. Jack kicked the boxes. They were all empty. “Unpacked by smugglers years and years ago!” said Jack. He shone his torch round the cave. “Where do we go from here?” he wondered. “Ah, look - is that a door or something over there?”

“Yes,” said Mike, who was nearest. “A good solid oak door too, fitted with bolts! I say, what a shame if it’s locked.”

He tried it - but it was not locked. It swung heavily into the cave, showing beyond it a narrow passage cut out of the rock itself.

“Here’s the passage!” cried Mike, in the greatest excitement. “I say! Isn’t this thrilling?”

“Mike, don’t make such a row,” said Jack. “We don’t know if anyone is coming down the passage or not, and if they should be, they’ll hear us easily! Let me go first. My torch is the brightest.”

He went up the dark, damp passage. It was so low in places that the children had to put down their heads in case they were bumped. The passage wound round and round and in and out, always going uphill, sometimes quite steeply. After a while it was not cut out of the rock, but out of sand and soil. It was quite dry by the time they had gone a few hundred yards.

Except for the noise that their feet made now and again the children were perfectly quiet. Presently they came to a wider piece of the passage and this widened out so much in a few moments that it became a kind of underground room. Here were more boxes, larger ones and much stronger looking. All were empty.

“Think of the old-time smugglers sitting here and having a feast, opening the boxes and barrels, selling the goods, going off again in the middle of the night!” said Peggy, looking round. The children could imagine it all very well.

“Aren’t we nearly up to the Old House now, Jack?” asked Nora. “We seem to have come a long way, always going uphill!”

“I think we must be very near,” said Jack in a low voice, “That oak door over there in the corner must lead into the cellars, I should think.”

“Let’s open it and see,” whispered Mike. He took hold of the iron handle of the door and pushed gently. It opened outwards, and Mike looked through it. There was a flight of stone steps beyond, leading steeply upwards.

The children went softly up them. There were eighteen of them.

At the top Jack swung his torch around. They were in a dark, underground cellar, set round with shelves. Empty bottles stood in rows. Barrels stood in corners.

“This is the cellar of the Old House, I’m sure,” said Jack. “And look - there are the steps leading into the house itself!”

His torch showed a short flight of steps in the far corner, leading up to a door that stood ajar, for a faint crack of daylight came through.

“You stay here, and I’ll slip up and see if I can hear anything,” said Jack. The others stayed as still as mice. Jack went quietly up the steps. He swung the door a little farther open and listened.

He could hear nothing. He peeped through the door. A large stone-floored scullery lay beyond the door. Nobody seemed about at all. Jack tried to remember where the tower would be. Of course! It would be quite near the scullery - maybe a door would lead from the scullery into the tower, so that servants could take the meals there when necessary.

Jack slipped through the door and took a quick look round. Yes - there was a little stout door at the end of the big scullery, just like the door through which the children had gone into the tower! It must lead there.

Now that he had gone so far Jack felt as if he must go farther! He tiptoed through the scullery, and tried the little tower door. It opened! He slipped through and ran up the winding stairs of the tower. He went right to the top - and when he got there he stopped in amazement.

He could hear somebody crying inside the top room of the tower. It sounded like a child. Jack tried the door - but alas, that was locked! He knocked softly.

The person inside stopped crying at once. “Who is it?” said a voice.

But just as Jack was going to answer, he heard the sound of voices. Someone was coming up the tower stairs! What was Jack to do? He couldn’t hide in the room at the top! But perhaps there was time to hide in the room below - if only they didn’t come there!

He slipped quickly down the stairs and into the room below, which was roughly furnished with a rug and a chair and table, Jack hid behind the door.

The voices came nearer as the people came up the winding staircase. Jack trembled with excitement behind the door.

The footsteps stopped outside the room where Jack was hiding. “I’ll just see if I left my papers in here,” said the voice of sleepy-eyed Luiz. The door was pushed open a little farther, and Luiz looked in!

Jack was quite sure that Luiz would see him when he popped his head in by the door. His heart beat so loudly that he thought Luiz would hear it. But to his great astonishment and joy Luiz glanced over to the table by the window, and then shut the door and went on up the tower stairs.

“My papers are not there,” Jack heard him say to his companion. The boy could hardly believe that he had not been seen. He waited until he heard the door of the room above unlocked, and then he quietly opened his own door, shot down the stairs at top speed, ran through the little door into the scullery and down the cellar steps, falling in a heap at the bottom.

“Jack!” whispered Mike in surprise. “What’s the matter? What a long time you’ve been!”

“I was nearly caught!” said Jack, panting. “Tell you all about it in a minute. Let’s get out of this cellar down into that underground room. Hurry!”

They all climbed down the eighteen steps to the underground room. They were longing to know what had happened to Jack.

“Let’s sit down here for a minute,” said Jack. They sat down on the old boxes and barrels. “I’ll tell you what happened,” said Jack. “I tiptoed through the scullery to the door that leads into the tower from there - and slipped up the winding staircase to the top - but the top door was locked. And there was somebody crying behind it!”

“Crying!” said Nora, in surprise. “Is there a prisoner in the tower, then?”

“Must be,” said Jack. “And it sounds like a boy or a girl, too! Isn’t it mysterious?”

“Perhaps they’re not smuggling silks and things, then, but have got a prisoner,” said Peggy seriously. “Perhaps it was the prisoner they brought in last night by that motor-boat and took through the secret passage to the tower.”

“I think you’re right, Peggy,” said Jack. “Now we’ll have to find out somehow who it is!”

“Well, I should think the prisoner will look out of the tower window sometime!” said Nora. “We could borrow Dimmy’s field-glasses and keep a watch, couldn’t we? Then we should see what sort of a prisoner it is.”

“Good idea, Nora,” said Mike. “We could easily take it in turns to keep watch for that.”

“I feel jolly hungry.” said Peggy. “Isn’t it about time we had our dinner? All this exploring has taken ages. What’s the time, Jack?”