“I have a theory. I believe it is correct. But I do not know it. So I will not pollute your mind. I suspect more evidence will come to light over the next few days. Form your own theory, then come to me. We will see if we agree.”

I couldn’t really argue with that. Not knowing what he thought was frustrating, yes, but his reasoning made a lot of sense. In fact, the spymaster had begun to remind me of Master Benedict—and not just because he could be a bit strange sometimes, too. He’d also cautioned me against jumping to conclusions.

“What about the cipher?” Walsingham said.

“I’m pretty sure it’s Vigenère,” I said, “but I haven’t been able to figure out the key.”

“You’re familiar with Vigenère, then?”

“Yes, my lord. My master taught me. Master Benedict, I mean.”

“I understood. The key, or the message—can you tell me anything about them?”

The way he asked made me think he already knew something. “No, my lord… Can you?”

“Yes.” I half expected him to say again he wouldn’t tell me what. Instead, he said, softly as ever, “Sit at my desk.”

I did.

“In the drawer to your right, you will find a quill, ink, and paper. I want you to do an exercise.”

Another test? Inwardly, I sighed, but I did as he commanded. I also took the paper with the Vigenère square out from under my apothecary sash.

He looked at it briefly, then nodded in approval. “I want you to encode a simple message. A single word: ‘the.’ ”

I felt like saying That’s it? But dutifully, I wrote it down. “And the key?”

“The same word.”

“ ‘The’ again?”

“Correct.”

I wrote it out, the key over the message.

T H E

T H E

“Encode it,” the spymaster said. “And do it out loud.”

This seemed awfully pointless, but, title or not, he was my master now. “To encipher something,” I said, “we start with the first letter of the key, T, in the row, and the first letter of the message, T, in the column. Then go down and across, and we get… M.”

“Next we match the second letters,” I said. “H with H gets… O. Finally, E with E makes… I. So all together, we get MOI… wait.”

T H E

T H E

M O I

“MOI,” I said, surprised. “That’s the first three letters of the code!”

M O I U R H J B X A M G X B H B L L

“So it is,” the spymaster said. “And we see our mystery messenger has made a mistake.”

Walsingham stood and came around to my side of the desk. “Vigenère is said to be unbreakable,” he said. “Le chiffre indéchiffrable, they call it: the indecipherable cipher. So far, that has proved to be correct. But even with an unbreakable code, we may find clues. For where the code succeeds, sometimes people fail.