"Do you mean to tell me that you didn't write a note and put it under my door this morning saying that you were going to find Slinky and talk to him? Did you or didn't you?"

Penny nodded brightly. "Oh! That note, Jon! Of course I did, but I'd forgotten just for a moment that I'd written to you. I suppose I was thinking about him so much that when I saw the letter-box waggle I was sure it must be him."

"Well, don't let him catch us sitting here," Jon said. "Whenever he meets us it seems as if we're doing something silly - you with one shoe on and me carrying a great jug of water, for instance. Let's go outside in the sun and talk about it till breakfast. There's no sense in making him suspicious... But I would like to know if he wears rubber soles?"

Half-way through breakfast Mrs. Warrender said, "You'll both be ready for me at a quarter to eleven, won't you?"

"Ready, darling?" Penny asked innocently. "What for? We're always ready for you."

"Church," said her aunt. "And not in those clothes either."

Penny looked shocked. "You don't mean that I'll have to wear a hat, do you, Auntie? I never wear a hat now, you know. I don't think I can get mine on."

Jon sniggered at this last remark, but was quickly quelled as his mother turned on him.

"And Jon, too. In your blue suit, please, Jon. And a decent collar for once."

Penny was looking very worried.

"But Auntie, darling. I don't think we can both go this morning. Do you mind if one stays at home on guard? Perhaps the one who stays could go to Evensong, if that's what you think we ought to do!"

"What do you mean - on guard?"

"It's just a game, Mother. She doesn't mean anything really. We'll be ready for you."

When they were alone again Penny said, "Jon, I've just had an awful thought. Have you got the clue safe?"

He opened his pocket-book and glanced inside.

"Yes! It's there. Let's go to our room and have another look at the map. We've got some time yet before we need change."

He felt in his jacket pocket. "The key!" he gasped. "I haven't got it... I left it under my pillow..."

They dashed up together, but the key was still where Jon had left it when he had seen Penny's note pushed under his door.

"It's such an enormous key," Jon said as they climbed Penny's stair, "that it's awkward to carry around. It's heavy, but I'll have to do it."

Then he put the key in the lock and pulled the heavy door towards them.

"Now I've got to find the key of the tin box, but I know I've got that somewhere..."