Anne was right. There were several inner pages, of a different size and quality of paper, that had been sewn into the original book and torn out at some unknown date by some unknown person.

However, when Anne laid out Emily’s sketch of the mysterious markings next to the remaining corner of one torn page, it matched the fragment of design left behind almost exactly.

“How strange that you should choose this book amongst all the others on the shelves,” Emily said warily. “It is indeed a very strange coincidence and far too convenient to be trusted.”

“I did not choose it, though,” Anne said. “I did not take it from the shelves. It was here on the window seat with a few others. But this one was on the top of the pile, as if it had just been left there a few moments ago, and so I picked it up, and beneath it is a very old prayer book and this, A Botanical Study of English Trees.”

Emily looked at the disparate collection of books; she knew each one had been taken from opposite corners of the library and left here together with the very book they were seeking on top.

“These books have been left here for us to find,” Emily said. “They all have meaning. I’m sure of it. It must have been known that we would call upon this library, though I suppose it is not all that surprising, given that no other library close by is open to women.”

“Left by whom?” Anne’s eyes widened. “And for what purpose?”

“Perhaps by someone who knows the truth about the Top Withens child and wants to aid our discovery,” Emily said, frowning deeply as she tried to make the puzzle pieces fit. “Or by the fiend who made those marks upon the chimney! Who else would know what was hidden in this book and tear out the pages, perhaps for the purposes of some diabolical ritual?”

“And then,” Anne said, “after the discovery of the bones, returned to Ponden to ensure they had left nothing behind that might incriminate them. Except they have. They have left two half pages in the book, one with enough ink remaining to match with your drawing. And left out clear as day, when it would have taken many hours of looking otherwise and we could have missed it altogether.”

Emily sat back on her heels as the clouds thickened outside, dimming the late afternoon with the threat of more snow.

“Someone knows we took the stones,” she said. “Someone knows we use the library at Ponden a great deal, and knew we would be likely to come here. Someone has devised a way to leave this book out for us to find as . . . as an invitation. No, not an invitation. A challenge.”

“A challenge?” Anne asked. “A challenge to what?”

“Why, to catch them, of course,” Emily said.