Some days you could feel a portal coming on. To everyone else the day might be sunny and clear, but to us five the air would feel clammy and charged the way it does before a storm. You could sense the world building up to something, screwing itself to the sticking point. Then we would look at each other conspiratorially and pull our ears—that was the agreed-upon sign—and from that point on we’d be no good for anything else. The madness was on us, and we would fidget feverishly, unable to sit still or read or follow our lessons. Nothing else mattered until someone vanished and the tension finally broke.

On other days Fillory would wrong-foot everyone. You wouldn’t see it coming at all. You might not even be in the mood for it, but suddenly there it would be, and all you could do was give in to its spell as it tore you free of this world.

It was one of those days, the second kind, when it happened: a lazy Saturday when the summer sun seemed to be leaching all the energy from the world, leaving us listless and immobile. We couldn’t play, we couldn’t study, we couldn’t stop yawning. Even the effort of going outside to visit the giant, bug-eyed goldfish in the stone-rimmed pond in back of the house would have been unimaginable.

Fiona and I were in the library, which was a pleasant room, two stories high, with two movable ladders which when rolled into each other at a high rate of speed produced a very satisfying bang. But as a library it was largely useless. The books were locked away in cabinets—you could see their spines through metal grills, like a forbidden city hidden in the jungle, but you couldn’t get at them. As far as I knew no one could: the keys were lost.

There was exactly one book in the library that you could read—somehow it had escaped being incarcerated with the rest of them. It was a catalog of seashells, a huge volume I could barely lift, and its spine cracked like a pistol shot when you opened it. The photographs were black-and-white, but about one in fifty pages had been hand-tinted in full color, and those shells had a special vivid feel to them. A Fillorian feel.

That morning Fiona and I were leafing through it. The pages were thick and sticky in the heat; they were made of a special glossy paper that was almost rubbery, like the leaves of some huge tropical plant. As usual we debated the aesthetic merits of the various shells, and the possible poisonous properties of their various residents, until suddenly Fiona stopped. She’d slipped her hand under the next page, hoping it would be a colored one, but her fingers found only empty air. It was as though the book had suddenly become hollow.