The gate clanged shut behind me and I rounded the corner, making my way straight to the Poison Garden.

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.

A small, windowless room took shape as my eyes adjusted to the gloom. A glass enclosure sat directly in the center. Immediately above it, a cylindrical shaft as big around as a can of soda was cut into the ceiling. I peered into it, and while I could see some light from the outside, it wasn’t strong enough to penetrate all the way down.

I turned my attention to the waist-high enclosure. Hinges ran between panes of cloudy glass. I tried to open one, but it didn’t budge. I shone my light in and caught my first glimpse of what it contained. The strange plant bore an unmistakable resemblance to a human heart. My phone slipped out of my trembling hand and hit the floor with a loud crack.

I scrambled to pick it up as the flashlight flickered on and off. A spider’s web of cracked glass stared back at me as I checked the extent of the damage. I sighed. I should have stayed my ass aboveground.

Turing back to the enclosure, my light glinted off something set in the stone near its base. I pushed up my glasses and crouched to read the words engraved on a rusting placard.

ABSYRTUS HEART

I slowly stood, my gaze locked on the glass housing. The plant from the big book was real, and for whatever reason, Circe had put me through an entire scavenger hunt to find it. It was behind a locked gate, a locked door, and a gathering of toxic plants that would put most people in the hospital—if they lived long enough to get to one.

The confines of the room pressed in on me. The Heart stood within the enclosure like something out of a nightmare. The plant was rooted in a small circle of dirt ringed by shining black stones, and directly next to it was a second circle of dirt where nothing grew.

I searched for a way to open the glass and found a small keyhole marked by the same crest as the door above. Using the bone-white key with the ruby heart, I unlocked the case. Without the foggy glass in the way, I studied the plant. It was even stranger up close. It looked like the drawing in the big book, but it wasn’t pink and plump. It was crumbling and ashen. The artery-like stalk snaked into the bone-dry dirt. Without thinking, I reached out to touch one of the broken leaves. Maybe it would perk up like the plants in the shop back home.

My fingers had barely brushed the nearest leaf when a bolt of cold entered my arm like an electric pulse. I stumbled back, clutching my hand. A numbing ache spread into my wrist. I cried out, my voice echoing all around me. Panting, my heart racing, I fell against the wall. My hand felt like it was frozen in a block of ice. The pain was so much worse than when I cut myself dissecting the water hemlock, worse than anything I’d ever felt. It was the most toxic thing I’d ever come in contact with.

I quickly locked the enclosure and left, making sure to lock the metal door, too. My hand ached, and the cold had spread to my arm like ice was flowing in my veins. I rubbed the back of my hand, trying to push warmth into the tips of my fingers, but the pain of touching my own skin was agonizing. I paced the Poison Garden, shaking out my hand.

I was immune to the hemlock, to the poison ivy, and the crimson brush, but this thing—the Absyrtus Heart—had wounded me in a way I didn’t think was possible. Did this immunity have limits?

The pain held fast, refusing to retreat. I watched the time through the fractured glass of my phone’s screen. Only after thirty minutes that felt more like hours did the pain start to dissipate.

A gathering of blush-pink oleander overtook the confines of its plot and spilled across the ground and was crowding the hellebore, suffocating it. I decided to thin it right at that moment and try to put my mind somewhere else. I grabbed a mesh bag from one of the hooks in the garden wall and pulled up the oleander, stuffing it inside. I glanced back at the place in the wall where the door was hidden. I didn’t know what an Absyrtus Heart was or why it was in its own secret room, protected by enough plants to kill everyone in Rhinebeck a few times over. Marie said it was dangerous. She’d asked me not to open the door. I should’ve listened.

I took the oleander I’d collected and left the garden. My hand still ached as I made my way home. I wanted to keep that room locked up. If that was what Circe had wanted me to find, she’d gotten her wish. I saw it, but I wasn’t going back in there. Why hold on to a plant like that? Something that poisonous was dangerous, not that anybody could even get to it—but still, why chance it at all? Dread crept in and buried itself in my thoughts.