“What is it?” Alice said, picking the thing up. It was intricately carved, the cover inscribed with an hourglass surrounded by tiny gears and levers.

“Essentially what it appears to be,” Ending said. “Keeping track of time in other worlds can be a tricky business. This will tell you how long it has been here in the library.”

Alice found the catch and clicked the cover open. In addition to the usual hour, minute, and second hands, a long, thin needle was just below the seven. Days, she realized. Seven days until Geryon returns.

“You must be back before it reaches zero,” Ending said. “Or I will not be able to protect you from Geryon’s wrath.”

“I will,” Alice said, snapping the watch shut and putting it in her innermost pocket.

“Let’s go,” Ending said.

Alice fell into step alongside Ending, who hugged the bookshelves and managed to stay in their shadow. Brief flickers of light threw silver highlights across her dark fur.

“I will not pretend,” Ending said, after a moment, “that this journey will not be dangerous. I warned you our path would be difficult.”

“I know,” Alice said.

“I’m taking you to a portal-book that leads to a village of fire-sprites. They can be vicious creatures, but they have an agreement with Geryon. You should be able to secure their aid.”

“All right.”

“Elsewhere in their world is a wild portal, a rift between worlds not yet bound by a Reader’s touch. The fire-sprites can show you the way there. What we need is on the other side.”

“What exactly am I looking for?”

“A book, of course,” Ending said. “The trap is in a book called The Infinite Prison. It is in a place called the Palace of Glass, somewhere beyond the wild portal.”

Alice was beginning to wish she’d brought a notebook. “And I just have to find this book and bring it back?”

Ending nodded, then looked up at her. Alice had been getting better at reading the labyrinthine’s moods in the set of her huge eyes, and now she thought the cat looked uncertain.

“The Palace of Glass is a dangerous place,” Ending said. “It is said that anyone who goes there is driven mad, if they manage to return at all.”

“I’ll be all right,” Alice said, forcing a smile. “Ashes always says I’m half-mad already.”

“You must be careful.”

They’d come to the back of the library, where clusters of shelves hid the portal- and prison-books. Passing among them, Alice smelled mowed grass, hot metal, and baking bread, and heard the roar of a crowd and strange, alien music.

Ending stopped. “This is where you’ll find the book that will take you to the fire-sprites. You will probably want to remove your shoes and socks.”