The Blackthorn Key

The cover was engraved with an image of a serpent swallowing its own tail. Tom and I glanced at each other. The drawing was identical to the snake that ringed the mural in the crypt.

“This is the ouroboros,” Isaac said. “It is the symbol of the Prima Materia. As it circles upon itself, so do we understand that the Prima Materia is the heart of the whole universe. All things, all life, stems from the First Matter. If you could access that Matter, then you, too, could direct it. This is the true goal of the alchemist.

“Apothecaries have already discovered many of God’s lesser powers. Silver heals. Aloe soothes. Oil of vitriol dissolves. Yet all of these are only shadows of the Prima Materia. Imagine the remedies you could create if you knew its secrets. Perhaps you could even prevent death itself.”

“This is what Master Benedict was looking for,” I said.

“Yes. You, too, I think.”

That surprised me. “I don’t know anything about it.”

“Not yet. But if Benedict sent you here, then he wished for you to understand.”

“He showed us how to find the door under the—” I began, but Isaac held up his hand.

“Stop,” he said. “It’s not for me to know where Benedict worked. I am no apothecary; I only keep the library. There are secrets we don’t share, even among ourselves. In this way, we protect the brotherhood from those who would misuse our discoveries.”

I thought of the Cult’s victims. They’d been tortured for information. But if each man only knew a piece of the puzzle, all the killers would be able to get from them were scraps that led obscurely to the next man in the line. It hadn’t stopped the killers, but it had delayed them for months, until they’d finally reached my master. He’d poisoned himself precisely so he couldn’t be forced to tell Wat what the boy wanted to know. He’d kept his final secret for me alone.

“Aren’t you worried they’ll find out about you?” I said.

“This library is my purpose in life. I cannot leave it.” Isaac shrugged. “As always, the future is in God’s hands. If they come for me, then that’s what will be.”

Not if I could help it. “We found a sealed door. Master Benedict said you had the key.”

Isaac returned to pushing the ladder, moving farther down the aisle. “The symbols you described earlier are alchemical. They represent instructions, written in code to keep secrets from prying eyes. Except the first symbol you mentioned, the downturned sword. That is not an instruction. It is the emblem of Michael, the Archangel.”

Tom shivered. So did I. “Is this . . . are alchemists the Cult of the Archangel?” Tom said.

“There is no Cult of the Archangel,” Isaac said.

I looked at Tom, who seemed just as confused as I was. “But . . . how can that be? These murders—”

“Are the acts of evil men. Yet their purpose has nothing to do with any cult. At least not in the sense people above use the word.” Isaac waved a hand at the books surrounding us. “Keeping our discoveries hidden isn’t the only reason we work in secret. Alchemists have, in the past, been accused of terrible crimes: treason, heresy, witchcraft. But we who search for God’s gifts to His servants are not murderers. It is the killers themselves who steal that name, spreading fear and lies, wrapping holy work in something sinister. In this way, they obscure their true motives.”

I thought of what Oswyn had said to me. “You said that alchemists are searching for knowledge to make the world better. I was told the Cult—the killers—wanted power.”

“So they do.” Isaac stopped pushing the ladder and looked up. “There. Third shelf from the top. The tome with the blue spine. Go ahead.”

I climbed the ladder and pulled the book he’d indicated from the shelf, bringing it back down.

“Open it,” Isaac said.

Tucked inside the back cover was a piece of parchment. On it was a chart, written in Master Benedict’s hand. Symbols, rows of them, were scrawled down the paper, a label beside each one.