“It was our field-glasses,” said Julian. “They are such fine ones. It’s a good thing you did get to the window for a breath of air or we’d never have found you!”

“Julian — I can hear a noise,” said Jo, suddenly. She had ears like a cat, able to pick up the slightest sound.

“Where?” said Julian, turning sharply.

“Downstairs,” whispered Jo. “Wait — I’ll go and see.”

She slipped out of the door and down the steep little stairs. She came to the door at the bottom, the one that led into the gallery.

Yes — someone was coming! Coming along the gallery too. Jo thought quickly. If she darted back up the stairs to warn the others this newcomer might go up there too, and they would all be caught. He could bolt the door at the top and would have six prisoners instead of one! She decided to crouch down on the floor of the gallery a little beyond the door that led upwards.

Footsteps came loudly along the gallery and up to the door. Then the stranger obviously found the door unbolted, and stopped in consternation. He stood perfectly still, listening. Jo thought he really must be able to hear her heart beating, it was thumping so loudly. She didn’t dare to call out to try and warn the others — if she did they would walk straight into his arms!

And then Jo heard Julian’s voice calling quietly down the stone stairs. “Jo! Jo! Where are you?” And then, oh dear, she thought she could hear Julian coming down the stairs to find her. “Don’t come, Julian,” she said under her breath. “Don’t come.”

But Julian came right down — and behind him came Terry-Kane and Dick, with the girls following with Timmy, on their way to escaping.

The stranger down at the door was even more amazed to hear voices and footsteps. He slammed the door suddenly and rammed the stout bolt home. The footsteps on the stairs stopped in alarm.

“Hey, Jo! Is that you?” called Julian’s voice. “Open the door!”

The stranger spoke angrily. “The door’s bolted. Who are you?”

There was a silence — then Terry-Kane answered. “So you’re back again, Pottersham! Open that door at once.”

Oho! thought Julian, so the other scientist is here too — Jeffrey Pottersham. He must have got Terry-Kane here by kidnapping him. What can have happened to Jo?

The man at the door stood there as if he didn’t quite know what to do. Jo crouched down in the gallery and listened intently. The man spoke again.

“Who set you free? Who’s that with you?”

“Now, listen, Pottersham,” said Terry-Kane’s voice, “I’ve had enough of this nonsense. You must be out of your mind, acting like this! Doping me, and kidnapping me, telling me we’re going to go off by fishing-boat to the Continent, and the rest of it! There are four children here, who saw my face at the window and came to investigate, and…”