"

"William, I am inspired. Stand by." He took down the Reverend Theodore
Ussher's classic work, looked at it with a happy smile for a moment, and
then gave it to Bill.

"Here, hold Ussher for a bit."

Bill took the book obediently.

"No, give it me back. Just go out into the hall, and see if you can hear
Cayley anywhere. Say 'Hallo' loudly, if you do."

Bill went out quickly, listened, and came back.

"It's all right."

"Good." He took the book out of its shelf again. "Now then, you can hold
Ussher. Hold him in the left hand so. With the right or dexter hand,
grasp this shelf firmly so. Now, when I say 'Pull,' pull gradually. Got
that?"

Bill nodded, his face alight with excitement.

"Good." Antony put his hand into the space left by the stout Ussher, and
fingered the hack of the shelf. "Pull," he said.

Bill pulled.

"Now just go on pulling like that. I shall get it directly. Not hard,
you know, but just keeping up the strain."

His fingers went at it again busily.

And then suddenly the whole row of shelves, from top to bottom, swung
gently open towards them.

"Good Lord!" said Bill, letting go of the shelf in his amazement.

Antony pushed the shelves back, extracted Ussher from Bill's fingers,
replaced him, and then, taking Bill by the arm, led him to the sofa and
deposited him in it. Standing in front of him, he bowed gravely.

"Child's play, Watson," he said; "child's play."

"How on earth--"

Antony laughed happily and sat down on the sofa beside him.

"You don't really want it explained," he said, smacking him on the knee;
"you're just being Watsonish. It's very nice of you, of course, and I
appreciate it."

"No, but really, Tony."

"Oh, my dear Bill!" He smoked silently for a little, and then went on,
"It's what I was saying just now a secret is a secret until you have
discovered it, and as soon as you have discovered it, you wonder why
everybody else isn't discovering it, and how it could ever have been a
secret at all. This passage has been here for years, with an opening at
one end into the library, and at the other end into the shed. Then Mark
discovered it, and immediately he felt that everybody else must discover
it. So he made the shed end more difficult by putting the croquet-box
there, and this end more difficult by--" he stopped and looked at the
other "by what, Bill?"

But Bill was being Watsonish.

"What?"

"Obviously by re-arranging his books. He happened to take ou