No one knows where this transitional world is. It may be an alternate plane of existence, or a place between planes, interleaved between them like a flower pressed between pages, or a master plane that contains all planes—the spine that gathers the pages and binds them together. To the naked eye it looks like a deserted city, an endless series of empty stone squares, but it serves as a kind of multidimensional switchboard. In the center of each square is a fountain. Step into one of them, the story goes, and you’ll be transported to another universe. There are hundreds of different squares, possibly an infinite number, and a corresponding number of alternate universes. The bunnies call this place the Neitherlands—because it’s neither here nor there—or sometimes just the City.

But the most important point, Penny said, is that at the end of The Wandering Dune Helen hid all the buttons somewhere in her aunt’s house in Cornwall. She felt they were too mechanical, they made the journey too easy. Their power was wrong. You shouldn’t be able to just go to Fillory whenever you wanted, like catching a bus, she argued. A trip to Fillory had to be earned, that had always been the way. It was a reward for the worthy, bestowed by the ram-gods Ember and Umber. The buttons were a perversion of this divine grace, a usurping of it. They broke the rules. Ember and Umber couldn’t control them. Fillory was fundamentally a religious fantasy, but the buttons weren’t religious at all, they were magical—they were just tools, with no values attached. You could use them for anything you wanted, good or evil. They were so magical they were practically technological.

So she hid them. Jane was inconsolable, understandably enough, and tore up half the property looking for them, but according to The Wandering Dune she never found them, and Plover never wrote any more books.

The Wandering Dune ends in the summer of 1917, or possibly 1918; because of the lack of real-world detail it’s impossible to date it precisely. After that the whereabouts of the buttons is unknown. But try a thought experiment, Penny suggested: How long could a box of buttons hidden by a twelve-year-old girl plausibly have stayed hidden? Ten years? Fifty? Nothing stays hidden forever. Wasn’t it possible—even inevitable—that in the decades that followed a maid or a real estate agent or another little girl would have found them again? And that from there they would have made their way onto the magical gray market?

“I always thought they were supposed to be lapel buttons,” Richard said. “Like a pin. Like ‘I Like Ike.’ ”