“Oh, it dries up. Falls into disrepair. It’s a mysterious process, but consistent with the integrity of the Neitherlands as a whole, so we allow it to happen.”

“Here’s what I’m wondering: could the tail wag the dog, so to speak? What if you repaired the fountain? Rebuilt it or replumbed it or what have you? Would that bring a dead world back to life?”

Penny thought for a minute, his lips moving silently. He walked the length of the ballroom and then back to where the rest of them stood.

“It’s not as stupid as it sounds,” he said, “but no. You couldn’t bring it back that way. You could wag the tail, but the dog would still be dead.”

Eliot nodded sadly.

“That was my last idea. I didn’t really expect it to work.” The fire had gone out of him. “Look, this is going to take forever. Let’s just go straight to the fountain.”

“I need to do something first,” Plum said. “Watch this: a magic trick.”

She’d seen it almost as soon as they walked in, she was just waiting for her moment. Plum walked right up to the enormous wall of books, feeling very small with the ranks of them towering above her. There was one narrow gap, a thin space where a single volume was missing. She took her great-grandfather’s memoir out of her bag.

Penny’s face went slack when he saw it.

“The Door in the Page,” he said, in a childlike voice. “It’s the Holy Grail of Fillory books. The last and rarest one. I’ve been hunting it for so long.”

She went to slide it in, paused, reflected, turned it the other way up, then shelved it. It fit perfectly, not just the size but the pattern: the spine was the perfect shade of a pale green, with a band of light blue near the top to fill in the last bit of the Lower Slosh, and a sliver of the Burnt River to go with it. It was so satisfying, like finishing an enormous jigsaw puzzle, that her fingers tingled, and she involuntarily let out a breath.

She was playing her part in the Chatwin story now. No more lingering in the wings, she was onstage, in the thick of it. She’d done what she could: she had brought Rupert home, or as close as he would ever get.

“Hey—Penny, is it?” Plum said. “That ought to pay for Quentin’s library fines, don’t you think? Or Alice could just punch you again, it’s all good.”

But Penny’s attention was completely occupied by his new acquisition. He went trotting up to it—half running across the shiny ballroom floor—and slid it gingerly out again, touching only the upper edges of its pages in order to spare the spine. He let it fall open and sniffed the paper.

“How did you get this?”