The Blackthorn Key (28 page)

“We already know this is mercury,” I said, pointing to the hole on the left. “The one at the top is . . .”

“. . . air?” I said, puzzled.

Tom reached up and poked his finger in the hole. “Isn't there air in here already?”

“Maybe that's the trick.” I turned to the workbenches with the ingredients. “Nothing's supposed to go in there. But if you don't have the key, you'd put different things in to try to crack it. So the lock won't work.”
Pretty clever
, I thought.

“All right,” Tom said. “Then what's the last one?”

There were three symbols to match.

A triangle, pointed down.
Water.

A curious ladder with a strange zigzag drawn at the bottom.
Mix.

A circle, a horizontal line cutting through its center.
Salt.

Water, mix, salt.

“Does that mean . . . salt water?” Tom said.

“That's what I'd guess,” I said. Air on top, mercury on the left, salt water on the right.

We got ourselves ready. I poured water up to the notch in one beaker. I dumped a heaping scoop of salt into it with the spoon on the other table. I stirred it, leaving a cloudy white liquid. A second beaker, filled with mercury, went to Tom.

We stood in front of the dragons. I gave Tom a nod.

Slowly, he poured the mercury in. We heard the faint
thunk
from behind the plate.

I tipped the salt water. It splashed down inside.

Nothing.

“Did we—”

Clack
.

The wall unsealed. A seam appeared, ringed around the inside of the
ouroboros
. The torch flickered as air rushed through it, whispering in our ears like breath.

The center of the mural swung open. The Archangel Michael beckoned.

I stepped inside.

A new, wide corridor was behind the seal. Here there were no nooks carved in the walls, no more ancient bones, just solid stone. The passage went another twenty feet. It ended in a wooden door.

“Look,” Tom said.

He was staring at the back of the mural. It was glass, so we could see the mechanism behind it, like the design inside my puzzle box. On the right, the mercury held down a lever attached to the lock at the side. On the top, where we'd left nothing but air, was another lever. If anything had been poured inside, it would have slammed down a counterweight, forcing the lock to stay closed.

But the most amazing thing lay opposite the mercury. The salt water I'd poured had gone into a ceramic jar. At its top, between two metal prongs, sparks crackled, brighter than those from a tinderbox. They looked like tiny lightning strikes. With each one came snaps, like baby thunder.

Tom crossed himself. “What in God's holy name is that?”

We stared at it in wonder, but the light lasted only a few seconds more. The salt water leaked out through tiny holes in the bottom of the ceramic jar, and ran down the glass through a copper tube into a flat pan behind the door. The sparks stopped, and the lock clacked shut. The mercury drained through a second tube into a glass jar beside the pan. When there was no longer enough weight to keep the lever down, it reset. I worried we might get trapped behind
the mural until I saw there was a handle on this side. We wouldn't need the ingredients to get out.

We went down the corridor to the final entrance. There was no puzzle here, and no key, just a plain iron latch on a plain wooden door. I pushed it open. The light from our torch filled the workshop beyond, and my heart swelled.

I felt like I was home again.

An oven exactly like ours was in the corner: iron curved like a flattened onion, enormous stacks of wood and coal beside it, the flue piercing the stone ceiling. Opposite it was a still, a giant beaker collecting drips below. The benches were covered with half-finished experiments. The shelves on the walls were laden with books, papers, and scrolls that spilled down to the floor. An ice vault was set into the flagstones beside the still, and next to that, a pendulum clock ticked on top of a stool. I hugged my arms to my chest and felt my master's presence.

Not everything was the same. There were additional chambers, one on each of the three other walls. Judging from the jars inside, the ones to the right and the left were stores for ingredients. From where I was standing, I couldn't see into the room opposite the door.

“What are these?” Tom said.

Behind us, wood planks were fixed to the stone, with
rows of nails hammered into them. From the spikes hung several pages, scrawled with words, diagrams, and symbols. A thick black slash was inked over most of them.

“Failures,” I said. “These are recipes. The slash means they didn't work.”

Most of the papers were Master Benedict's, but not all of them. Some of the work showed Hugh's handwriting, thick and loopy. There were other authors I didn't recognize: at least three more, judging by the different hands.

“This was their secret lab,” I said. “This is where Master Benedict went all those nights.”

More papers rested beneath the nailed board, stacks of them. There had to be thousands of pages here. In the first stack, as on the board, most of the papers were in Master Benedict's handwriting. As I went through the others, the handwriting changed, the parchment growing increasingly brittle. I counted at least a score of different authors before I stopped. This was years of work, decades. Maybe centuries.

“Christopher.”

Tom stared at the chamber opposite the entrance. In front of it, on the floor, dark brown streaks smudged across the stone. Beside them was a bucket filled with rags, each one stained the same.

It was blood. Dried blood. A lot of it.

The door to the chamber was open. The walls around it were charred. Inside the chamber was the same sooty black, and there were scars, too, chunks of stone carved away. A dented iron table rested in the center of the room. On top of it was a heavy beaker, glass, its wide mouth stopped with cork. It was filled to the three-quarter mark with a yellowish liquid.

I picked it up. The liquid inside sloshed around, kind of goopy.

“What is it?” Tom said.

I shook my head. “I don't know.”

He peered at the liquid as I turned the beaker over, watching it drip down the sides. “Looks like oil.”

I popped open the cork and dipped a finger in. It felt like oil, too. The smell of it was vaguely fruity, and exotic, like those bananas imported from tropical islands. I touched my finger to the tip of my tongue.

“It's sweet,” I said, surprised. It made my tongue tingle, like a syrup of hot pepper. I'd never tasted anything quite like it before.

I put the cork stopper back in and gave the beaker to Tom, who studied the liquid more closely. I returned to the workbench. Papers were scattered everywhere, covered in my master's
handwriting. Beside them was a long loop of cannon fuse. Below the bench, two more coils of fuse were stacked, more than I'd ever seen in our shop. I looked at the chamber we'd taken the beaker out of, at the charring that covered the walls.