“Children!” said Pottersham, taken aback. “What in the middle of the night! How did they get up to this tower? I’m the only one that knows the way in.”

“Pottersham, open the door!” shouted Terry-Kane, furiously. He gave it a kick, but the old door was sturdy and strong.

“You can go back to the tower, all of you,” said Pottersham. “I’m going off to get fresh orders. It looks as if we’ll have to take those kids with us, Terry-Kane — they’ll be sorry they saw your face at the window. They won’t like life, where we’re going!”

Pottersham turned and went back the way he had come. Jo guessed that he knew the same way in as they had happened on. She waited until she felt that it was perfectly safe, and then she ran to the door again. She hammered on it.

“Dick! Dick! Come down. Where are you?” She heard an answering shout from up the stairs behind the door, and then Dick came running down.

“Jo! Unbolt the door, quick!”

Jo unbolted it — but it wouldn’t open. Julian had now come down too, and he called to Jo. “Turn the key, Jo. It may be locked too.”

“Julian, the key’s gone!” cried Jo, and she tugged in vain at the door. “He must have locked it as well as bolted it — and he’s taken the key. Oh, how can I get you out?”

“You can’t,” said Dick. “Still, you’re free, Jo. You can go and tell the police. Buck up, now. You know the way, don’t you?”

“I haven’t got a torch,” said Jo.

“Oh dear — well, we can’t possibly get one of ours out to you,” said Dick. “You’d better wait till morning, then, Jo. You may lose yourself down in those dark passages. Yes — wait till morning.”

“The passages will still be dark!” said poor Jo. “I’d better go now.”

“No — you’re to wait till morning,” said Julian, fearing that Jo might wander off in the strange passages, and be lost for ever! She might even find herself down in the dungeons. Horrible thought.

“All right,” said Jo. “I’ll wait till morning. I’ll curl up on the gallery here. It’s quite warm.”

“It will be very hard!” said Dick. “We’ll go back to the room upstairs, Jo. Call us if you want us. What a blessing you’re free!”

Jo curled up on the gallery, but she couldn’t sleep. For one thing the floor was very hard, and the stone was very very cold. She suddenly thought of the little room where they had seen the pitcher, the dagger and the chocolate wrapping-paper. That would be a far better place to sleep! She could lie on the bench!

She stood up and thought out the way. All she had to do was to go round the gallery till she came to the little door that opened on to the corkscrew staircase leading from the gallery to the little hidden room.