That was a fair point. And yet… “I think that’s about to change,” I said.

“Why?”

“Because I’m pretty sure this third message is a warning.”

CHAPTER 31

I PULLED THE CRUMPLED LETTER from beneath my doublet and spread it on the table. Everyone leaned in to read it.

Low the swan flies, ever lower,

Dancing, singing overhead,

Slow the song plays, ever slower,

Oh, too late—now they’re all dead.

“You know what this means?” Sally said.

“Part of it,” I said, and I turned to Isaac. “Do you remember that key my master left with you for me to find? The first day I came here, last spring?”

“I’m old, Christopher, not senile,” he said.

“Right. Sorry. Um… that page, with the alchemical symbols. Did my master ever write down any more of them?”

Isaac regarded me for a moment, frowning. Then he turned to Sally. “Did you find that book I asked you to bring up? The one with the blue spine?”

She nodded and pulled it from the stack beside her. He motioned to give it to me.

“Look in there,” Isaac said. “You’ll find a few pages tucked inside.”

I flipped through the book. It was an ordinary work on theology, but pressed between several of the pages were leaves of paper. Each one was covered in symbols, Master Benedict’s handwriting beside them, giving definitions.

“This is it,” I said.

Sally looked at Isaac, puzzled. “How did you know Christopher would ask for those?”

“The Templar’s confession.” Isaac finished the last of his coffee. “Do you remember what poor Mr. Egerton said? ‘It is the responsibility of the recipient of the message to know how to decipher the code.’ That’s only possible if the recipient—in this case, Christopher—already knows what he’s looking for.

“The first letter was Vigenère. The second, Alberti’s disk. The books I asked you to collect hold many of the ciphers Benedict taught him.” Still, he looked troubled.

“What’s the matter?” Sally said.

“These Templars,” Isaac said slowly, “seem to know quite a bit about Christopher—and Benedict. In particular, what Christopher has been taught. I’m not sure how that’s possible.”

That made me pause. I hadn’t really thought too hard about the codes themselves. After what happened in Paris, the Templars would have known I could solve ciphers.

And yet they’d only seen me decipher Vigenère. I’d never used Alberti’s disk before, beyond what my master had shown me.

So how did they know I even had the device?

Another question without an answer—and no way of getting one. I forced myself to put it aside for the moment. Instead, I scanned Master Benedict’s notes, looking for a particular symbol that matched one in the message.

“How did you know what to look for?” Tom asked me. “Have you seen these symbols before?”

“Well… the middle glyph does look like an alchemical symbol,” I said. “But the real clue was in the riddle. The swan.”