The front section of the garden had come alive since Karter and I had started working on it. The foliage was lush, vibrant, and more animated than I’d ever seen it, shifting and reaching as I went to the moon gate. I braced myself for the chill of the airborne poison as it hit the back of my throat and burned the inside of my nose. It only took me a second to recover.

Where the front half of the garden had been every shade of evergreen, olive, and emerald, the Poison Garden had also come alive like never before. Blankets of belladonna intertwined with wide leaves in rippling shades of black, sable, and obsidian—just as vibrant, just as prismatic as their benign counterparts. Deadly crimson thorns protruded from the arms of Devil’s Pet, which had doubled in size and now twisted through the overgrown foliage.

I walked to the center of the rear wall. The Devil’s Pet cinched itself up, revealing the door. I held the key in my trembling hand, and its heart-shaped stone glinted as I inserted it into the lock and twisted until it clicked.

The door groaned as I pushed it open. I’d expected another garden or a storage area, but it was a darkened enclosure no bigger than a hall closet. The smell of damp earth permeated the air. The room had a slanted roof made of the same stone as the walls and was completely covered from floor to ceiling with tangles of poison ivy, stinging nettle, and, to my astonishment, crimson brush.

Crimson brush was supposed to be extinct. I’d only ever seen black-and-white photos of it, taken in the late 1800s when a single sprig remained in the British Museum. Its star-shaped blooms burst from their three-leafed seats and emitted a rust-colored pollen. It should have caused sores to open on my skin and closed up my throat and eyes, but once again, I was unaffected aside from an ice-cold chill. I fanned the cloud of pollen away and the brush shrank back, as if it had realized its mistake.

I pulled out my phone and turned on my flashlight, sweeping it around. The tangle of crimson brush shifted, revealing a narrow stairway that led down. Only the top few stairs were visible. I inched closer and held my phone at arm’s length. The weak column of light illuminated the floor of the room below. The steps were covered in a layer of slick green algae. Water trickled down the walls, running off in delicate rivulets, dampening the stone beneath my feet. Gripping my phone, I descended into the dark.