"It's blank."

"Hold it up to the light."

"Oh, yes. I see. That's very clever. Is this how you used to pass notes in school?"

"No, it's a little obvious when you have to raise the page up like that."

"Yes, I suppose it is. The page doesn't have to be blank, does it? You could write something mundane on here. A shopping list, maybe, or a note. 'I miss you, but I don't remember why.' Something like that."

"You could. A lot of old manuscripts were done like that. Secrets were written between lines and in the margins. Most of the old knowledge has been preserved that way."

"Listen to you. 'The old knowledge.'"

"What?"

"You make it seem so mysterious, so clandestine."

"But it was. This is how the heretics hid in plain sight. They would author epistles and monographs that seemed to uphold the virtues of the Church, but hidden along the outer edge of the page were lines and lines of blasphemy.

"The alchemists, too, they passed their secret recipes along via hidden writing. That's why the original manuscripts are so highly prized. Sure, you could make copies, but they were just strange writings—treatises that seemed to almost make sense, but not quite. That was the whole point of the hidden key: without it, the book seemed to work, in theory; but in practice, the text—as written—never worked."

"What about you and your friends. The oneironauts. Do you leave messages for each other?"

"We don't share the same variation of the Oneiroi."

"Why not? You're sharing mine."

"That's different."

"Is it? How so?"

"It's just . . . not done like that, Nora. We don't intrude on each other's dreams. It's, well, rude . . . and dangerous."

"But you could? You just don't."

"That's right."

"Does everyone think the same way? Is this one of those laws no one ever contemplates breaking?"

"Yes."

"Are you sure?"

"Well, it's not like I've signed a contract, or we've all taken a blood oath or something. Wandering into another oneironaut's dreams is just not done. It's always been that way."

"And you all accept that?"

"Yes, Nora. We do."

"But if someone didn't, how would you know? The dream would be like this piece of paper: blank, unless I know how to look at it correctly."

"Yes, for the sake of argument, that would indeed be the case. Unless you had the key, unless you knew the way, you couldn't see the hidden content."

"Turn around."

"What?"

"Turn around. Look at the wall behind you."

"There's nothing—"

"Do you see it now?"