“Yeah, it’s in the Poison Garden. I haven’t cultivated it. I’ve never seen anything like it. It’s poisonous—the most toxic thing I’ve ever touched.”

“You touched it?” Marie asked.

I shrank back. “I thought it would be like all the other poisonous stuff I can touch, but it felt like my hand was gonna fall off.”

Marie crossed her arms over her chest. “I need you to stop trying to get yourself killed.”

I gently squeezed her arm. “You were right about it not being like the other plants.” I flipped through the drawings in the book. “All the other plants have instructions, but not the Heart. I wouldn’t have known how to cultivate it, but now I do.”

“What changed?” Karter asked.

“I found a document and Marie helped me get it translated. It’s old. Ancient, actually. It told the story of Medea.” I gestured toward the painting on the wall. “She was from a place called Colchis, the same name of my birth family.” I had to say out loud what my gut told me was the truth. “I think—I think I’m related to her.”

Marie gasped so hard she started to cough.

“Wait, wait, wait.” Karter shook his head. “You really think your family tree goes back that far?”

“It makes sense,” I said. “I thought Circe and Selene were obsessed with her, but it’s not that. It’s normal to have portraits of your relatives hanging up, right?”

Karter shrugged. “I guess?”

“And she was a poisonist,” I said.

“What’s a poisonist?” he asked.

“Someone like me,” I said. “Somebody who can work with poisonous plants and not be affected. All the things I’ve found out about this house and my family lead to Medea and to that.” I pointed to the drawing of the Heart. “The people I’ve met since I’ve been in Rhinebeck know it’s out there, but they don’t mess with it. They don’t even want to talk about it, like it’s an open secret. They make it seem like it’s my responsibility. Medea was the Heart’s original caretaker. She could do everything I can.” I stood up. There was only one thing I wanted to do. “Come on. I want to look at the Heart again.”

Marie started to protest, but I headed downstairs before she could say anything. Karter and Marie followed me out the front door and across the lawn. I didn’t even pause as I approached the hidden trail. The vines and branches parted.

“Stay close to me,” I reminded Karter.

“I know the drill.” He glanced at Marie. “What about her?”

“I’m good,” said Marie.

I hadn’t asked about the limits of her power. She didn’t seem too worried for her safety, so I pressed on.

About halfway to the garden, I noticed the shadows growing long. The sun had been at the horizon when we’d ducked onto the path, but after the email from Professor Kent and what I’d learned from that ancient document, I couldn’t wait another day, another hour.

When we came into the clearing, I took out my phone and switched on the flashlight. Karter did the same. The trees leaned away to reveal the gate and I unlocked it, nudging him and Marie through. It clanged shut behind us.

Even in the encroaching darkness, I could see Marie’s eyes alight with wonder. She’d been honest with me when she said she’d never been inside the garden.

“Wait till you see this,” I said, pulling her toward the Poison Garden.

Devil’s Pet wound itself around the moon gate.

“We are going straight to the back wall,” I said. I turned to Karter. “Wait here until I tell you to come through.”

“I could . . . ​help,” Marie offered. She made a motion like she was picking up a baby and rocking it in her arms.

I looked at her and then to Karter. She was suggesting she could pick him up and rush him through the Poison Garden. I had to bite the inside of my cheek to keep from laughing. How ridiculous would it be to see Karter carried around like a small child? He was way too scary to let that happen, so I shook my head no.

“How could you help?” Karter asked.

Marie pretended she didn’t hear him, and he shoved his hands in his pockets, glancing around nervously. I walked through the Poison Garden and stopped in front of the rear wall. The vines pulled back, and I opened the hidden door. The crimson brush bloomed and pointed toward the door. I held up my hand. The plant retreated.

“Ready?” I called to Karter. “Hold your breath and run. Now!”

Karter sprinted forward, stumbling once and nearly falling flat on his face. Marie was suddenly there, hoisting him up and pulling him toward the door. They slid to a stop in front of me.

“Oh, wow,” Karter said, staring down at Marie. “You work out?”

I yanked him through the door and Marie slipped in after him. I stood between them and the crimson brush’s star-shaped blooms.

“Down there,” I said, gesturing to the stairs.

They disappeared below and I followed once I was sure the crimson brush wasn’t going to act up. I descended the stairs into the dank little room. Karter and Marie were both completely silent. The lights from our phones illuminated the small space. The plant stood in its glass enclosure. Karter leaned in and I quickly put my arm in front of him.

“This is the Absyrtus Heart,” I said. “It’s the deadliest plant I’ve ever come in contact with. I don’t want either of you to get hurt. You shouldn’t even be in here, but I had to show you this. It’s real. It exists.”

I examined the hole in the ceiling, and Karter followed my gaze.

“I think when the moon rises, it shines through there,” I said.

“What kind of plant grows in the dark?” Karter asked. “Don’t plants need sunlight?”

“Queen of the Night cacti only bloom in the dark.” I unlocked the glass door and we peered inside. “But this is something else.”

Marie stood as still as the shadows. “I don’t even know what to say.”

I’d felt the same way when I first saw it. If I hadn’t seen the shriveled stalk and crumbling leaves underneath it, I would have thought I was looking at a real human heart, somehow preserved.

For my AP Biology class, we’d taken a field trip to the museum and seen a human heart suspended in a jar of formaldehyde. We’d had to label the parts on a worksheet, and all those parts were there on the strange plant. The flat waxy plain of the right and left ventricles was pointed upward. The tangle of what might have been arteries snaked off the bottom and fed into long, thick stalks.