“Yes. And the library for choice. I mean for our choice. There are always servants going into dining-rooms. We shouldn’t have much of a chance of exploring properly in there. Besides, there’s another thing to remember. Mark has kept this a secret for a year. Could he have kept it a secret in the dining-room? Could Miss Norris have got into the dining-room and used the secret door just after dinner without being seen? It would have been much too risky.”

Bill got up eagerly.

“Come along,” he said, “let’s try the library. If Cayley comes in, we can always pretend we’re choosing a book.”

Antony got up slowly, took his arm and walked back to the house with him.