“Maybe he can tell us that!” said the other. And then, for the first time, George’s father heard how George had got there and why.

She told them how she had watched for Timmy in the glass room of the tower and hadn’t seen him — and that had worried her and made her suspicious. So she had come across to the island in her boat at night, and had seen where the men came from. She had gone down the tunnel, and kept on till she came to the cave, where she had found her father.

The three men listened in silence. “Well, you’re a tiresome nuisance,” one of the men said to George, “but my word, you’re a son to be proud of. It’s not many boys would have been brave enough to run so much risk for anyone.”

“Yes. I’m really proud of you, George,” said her father. He looked at her anxiously. She knew what he was thinking — what about his precious book? Had she been sensible enough to hide it? She did not dare to let him know anything while the men were there.

“Now, this complicates matters,” said the other man, looking at George. “If you don’t go back home you’ll soon be missed, and there will be all kinds of search-parties going on — and maybe someone will send over to the island here to tell your father you have disappeared! We don’t want anyone here at present — not till we know what we want to know!”

He turned to George’s father. “If you will tell us what we want to know, and give us all your notes, we will set you free, give you whatever sum of money you ask us for, and disappear ourselves.”

“And if I still say I won’t?” said George’s father.

“Then I am afraid we shall blow up the whole of your machines and the tower — and possibly you will never be found again because you will be buried down here,” said the man, in a voice that was suddenly very hard.

There was a dead silence. George looked at her father. “You couldn’t do a thing like that,” he said at last. “You would gain nothing by it at all!”

“It’s all or nothing with us,” said the man. “All or nothing. Make up your mind. We’ll give you till half past ten tomorrow morning — about seven hours. Then either you tell us everything, or we blow the island sky-high!”

They went out of the cave and left George and her father together. Only seven hours! And then, perhaps, the end of Kirrin Island!

Chapter Eighteen

Half past four in the morning

As soon as the men were out of earshot, George’s father spoke in a low voice.

“It’s no good. I’ll have to let them have my book of notes. I can’t risk having you buried down here, George. I don’t mind anything for myself — workers of my sort have to be ready to take risks all their lives — but it’s different now you’re here!”