The Blackthorn Key

The black spots, in the dragons’ mouths. I’d thought they were paint, like the rest of the mural. But up close, I could see each one was actually a small hole in the wall, the three of them together forming the corners of a perfect triangle. I peered into the one being eaten by the dragon on the left, but even with the torch, it was too dark to see anything. Against Tom’s urging, I poked my finger inside.

I couldn’t feel anything, either. There was a gap behind the wall, but the end—if there was one—was at least far enough away that my finger couldn’t reach it. I could tell one thing, though. From the smoothness of the hole, and its coolness on my skin, the wall wasn’t stone. It was iron.

Up close, the mural was even more remarkable. Hundreds of shapes and symbols were inscribed around the dragons. Some were simple, like circles and squares. Others looked more like alien letters of a forgotten language. As I stared at them, I noticed something. Near each of the holes in the dragons’ mouths, some of the glyphs were ringed with gold, so faint you could barely see it.

Gilded next to the serpent at the top was a triangle with a line across it, like the peak of a snowcapped mountain.



The dragon in front of Tom had three highlighted symbols: a triangle, upside down; a curious ladder with a strange zigzag at the bottom; and a circle with a horizontal line through its center.



The final dragon, in front of me, had a single golden glyph.



I stopped. I’d seen this one before.

This was the symbol for the planet Mercury. I looked back at the workbenches, and the ingredients that sat upon them. I took my puzzle cube out of my pocket and turned it around.

“What is it?” Tom said.

I touched the wall. “I think I know what this is. It isn’t just a painting.” I traced my fingers from the dragon to the hole. “I think this is a door.”





CHAPTER


21


TOM INCHED AWAY FROM THE mural. “A door?”

I pointed to the symbols above the holes. “I think this is what the ingredients on the tables are for. The liquids and powders, the beaker, the spoon. It’s like my present.” I held out the antimony box. “You pour the right thing in and it opens.”

“What’s the right thing?”

“Well, this symbol here is for Mercury, so I’m guessing it’s quicksilver.”

There was plenty of mercury in one of the jars on the table, more than I’d ever seen in one place before. I took one of the notched beakers and poured some of the quicksilver into it. The glass grew heavy as I filled it to the mark.

At the door, the beaker’s nozzle fit cleanly into the hole in the dragon’s mouth. I tilted it, letting the metal run out. With the last few drops, a faint thunk came from behind the mural.

“It worked,” Tom said.

But nothing else seemed to happen. I pushed on the wall. Tom joined me, putting his shoulder to it. It didn’t budge. We heard another thunk, as if something clicked back into place.

I stepped away from the mural. “There are two more holes,” I said. “We must have to put something in all of them to open the door.” And from the sound of it, we didn’t have much more than a minute to make it happen.

The symbols, with the right ingredients, were the key. I was amazed at how clever this was. It was much better than an actual key of iron or brass, which could be lost or stolen. With this door, if you were allowed in, you’d already know how to enter. Which we didn’t.

“What about the rest of the message?” Tom said. “Those letters, from the code in lemon juice. Maybe they tell you what the ingredients are.”

I pulled the parchment with the code from my pocket.

JSYYAALYUFMIYZFT

“Look,” Tom said. “Say the M is for ‘mercury.’ Then J is for . . . uh . . . ‘jam.’ Or something.”

If you ignored the part about jam, Tom’s idea was a good one. But there were two more holes, four more symbols, and my master’s message had enough letters to start a new alphabet. Even if Tom was right, I couldn’t count how many different combinations we’d have to try. We were lost.

Again.

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