All the same, Jo was willing to try. “I might be able to do it,” she said, slipping off one of her shoes.

“Put your shoe on,” said Dick at once. “You are NOT going to try any tricks of that sort. There isn’t even ivy for you to cling to.”

Jo put back her shoe sulkily, looking astonishingly like George as she scowled. And then, to everyone’s enormous astonishment, who should come bounding up to them but Timmy!

“Timmy! Wherever have you come from?” said George, in surprise. “There’s no way in except through the turnstile — and the door behind it is shut. We shut it ourselves! How did you get in?”

“Woof,” said Timmy, trying to explain. He ran to the good tower, made his way over the blocks of stone lying about and stopped by a small space between three or four of the fallen stones. “Woof,” he said again, and pawed at one of the stones.

“He came out there,” said George. She tugged at a big stone, but she couldn’t move it an inch, of course. “I don’t know how in the world Timmy squeezed himself out of this space — it doesn’t look big enough for a rabbit. Certainly none of us could get inside!”

“What puzzles me,” said Julian, “is how Timmy got in from the outside. We left him right outside the castle — so he must have run round the outer wall somewhere and found a small hole. He must have squeezed into that.”

“Yes. That’s right,” said Dick. “We know the walls are eight feet thick, so he must have found a place where a bit of it had broken at the bottom, and forced his way in. But — would there be a hole right through the whole thickness of eight feet?”

This was really puzzling. They all looked at Timmy, and he wagged his tail expectantly. Then he barked loudly and capered round as if he wanted a game.

The door behind the turnstile opened at once and the old lady appeared. “How did that dog get here?” she called. “He’s to go out at once!”

“We don’t know how he got in,” said Dick. “Is there a hole in the outer wall?”

“No,” said the old woman. “Not one. You must have let that dog in when I wasn’t looking. He’s to go out. And you too. You’ve been here long enough.”

“We may as well go,” said Julian. “We’ve seen all there is to see — or all that we are allowed to see. I’m quite sure there is some way of getting up into that tower although the stairway is in ruins. I’m going to ring up the Society for the Preservation of Old Buildings and ask them to put me in touch with the fellows who examined the castle last week. They must have been experts.”

“Yes. They would probably have a complete plan,” said Dick. “Secret passages, dungeons, hidden rooms and all — if there are any!”