“Marian? Have you—did my mother ever see this?” I couldn’t let it go. I couldn’t think about anything else.

Marian looked at me, her eyes strangely sparkling. “Your mother was the person who gave me the job.”

And with that, she disappeared in front of us through the illusionary grating, and down into the Lunae Libri below. Boo Radley barked, but it was too late to turn back now.

The steps were cold and mossy, the air dank. Wet things, scurrying things, burrowing things—it wasn’t hard to imagine them making themselves comfortable down here.

I tried not to think about Marian’s last words. I couldn’t imagine my mother coming down these stairs. I couldn’t imagine her knowing anything about this world I’d just stumbled onto, more like, this world that had stumbled onto me. But she had, and I couldn’t stop wondering how. Had she stumbled onto it too, or had someone invited her in? Somehow, it made it all seem more real, that my mother and I shared this secret, even if she wasn’t here to share it with me.

But I was the one here now, walking down the stone steps, carved and flat like the floor of an old church. Along either side of the stairs I could see rough stone boulders, the foundations of an ancient room that had existed on the site of the DAR building, long before the structure itself had been built. I looked down the stairs, but all I could see were rough outlines, shapes in the dark. It didn’t look like a library. It looked like what it probably was, what it had always been. A crypt.

At the bottom of the stairs, in the shadows of the crypt, countless tiny domes curved overhead where the columns jutted up into the vaulted ceiling, forty or fifty in all. As my eyes adjusted to the dark, I could see that each column was different, and some of them were tilted, like crooked old oaks. Their shadows made the circular chamber seem like some kind of quiet, dark forest. It was a terrifying room to be in. There was no way of knowing how far back it went, since every direction dissolved into darkness.

Marian inserted her key into the first column, marked with a moon. The torches along the walls lit themselves, illuminating the room with flickering light.

“They’re beautiful,” Lena breathed. I could see her hair still twisting, and wondered how this place must feel to her, in ways I could never know.

Alive. Powerful. Like the truth, every truth, is here, somewhere.

“Collected from all over the world, long before my time. Istanbul.” Marian pointed to the tops of the columns, the decorated parts, the capitals. “Taken from Babylon.” She pointed to another one, with four hawk heads poking out from each side. “Egypt, the Eye of God.” She patted another, dramatically carved with a lion’s head. “Assyria.”

I felt along the wall with my hand. Even the stones of the walls were carved. Some were cut with faces, of men, creatures, birds, staring from between the forest of columns, like predators. Other stones were carved with symbols I didn’t recognize, hieroglyphs of Casters and cultures I’d never know.

We moved farther into the chamber, out of the crypt, which seemed to serve as some sort of lobby, and again torches burst into flame, one after another, as if they were following us. I could see that the columns curved around a stone table in the middle of the room. The stacks, or what I guessed were the stacks, radiated out from the central circle like the spokes of a wheel, and seemed to rise up almost to the ceiling, creating a frightening maze I imagined a Mortal could get lost in. In the room itself, there was nothing but the columns, and the circular stone table.

Marian calmly picked up a torch from an iron crescent on the wall and handed it to me. She handed another to Lena, and took one for herself. “Have a look around. I have to check the mail. I may have a transfer request from another branch.”

“For the Lunae Libri?” I hadn’t considered that there might be other Caster libraries.

“Of course.” Marian turned back toward the stairs.

“Wait. How do you get mail here?”

“The same way you do. Carlton Eaton delivers it, rain or shine.” Carlton Eaton was in the know. Of course he was. That probably explained why he’d picked Amma up in the middle of the night. I wondered if he opened the Casters’ mail, too. I wondered what else I didn’t know about Gatlin, and the people in it. I didn’t have to ask.

“There aren’t too many of us, but more than you’d think. You have to remember, Ravenwood has been here longer than this old building. This was a Caster county before it was ever a Mortal one.”

“Maybe that’s why you’re all so weird around here.” Lena poked me. I was still stuck back on Carlton Eaton.

Who else knew what was really going on in Gatlin, in the other Gatlin, the one with magical underground libraries and girls who could control the weather or make you jump off a cliff? Who else was in the Caster loop, like Marian and Carlton Eaton? Like my mom?

Fatty? Mrs. English? Mr. Lee?

Definitely not Mr. Lee.

“Don’t worry. When you need them, they’ll find you. That’s how it works, how it always has.”

“Wait.” I grabbed Marian’s arm. “Does my dad know?”

“No.” At least there was one person in my house who wasn’t living a double life, even if he was crazy.

Marian issued a final piece of advice. “Now, you’d better get started. The Lunae Libri is thousands of times bigger than any library you’ve ever seen. If you get lost, immediately trace your steps backward. That’s why the stacks radiate out from this one chamber. If you only go forward or back, you have less chance of getting lost.”