The Mustard Seed Pact

I was eleven when the library’s basement corridor first hummed. It wasn’t a sound so much as a pressure—a low, insistent drone that vibrated through the soles of my sneakers and settled in my teeth. I’d been shelving returns for Mrs. Kessler, our gray-haired librarian who smelled of lavender and old paper. She trusted me, a quiet kid who never caused trouble, to handle the books that nobody else wanted: the brittle encyclopedias, the cracked volumes of regional poetry, the unmarked paperback with a cover that looked like a bruised sunset.

That book was the one that felt warm. I pulled it off the cart, and the hum spiked, just for a second. The title read *The Mustard Seed*, and inside, the pages were blank—except for one, near the middle, where someone had written in a neat, slanting hand: ‘When you feel alone, turn to page 47.’ I did, and there was a single sentence: ‘You will find her in the place where the walls remember.’ That night, I dreamed of a girl with hair the color of river silt and eyes like polished stones. She told me her name was Larkspur, and she was sorry for the noise.

Over the following weeks, Larkspur became my secret. She only appeared when I was in the library’s basement, that dim corridor with the lone flickering fluorescent tube. She’d whisper facts I couldn’t know: the mating call of the oilbird, the date the Colossus of Rhodes toppled, the recipe for a forgotten medieval remedy using mustard powder. She was gentle, like a hand resting on my shoulder, and she never asked for anything—until the day she asked me to bring a seed from the courtyard garden, a single mustard seed, and place it in a crack in the basement wall. ‘To keep my door open,’ she said. ‘So I don’t have to leave.’

I did it without thinking. The next week, Mrs. Kessler found me weeping in the basement, curled against the shelf where I’d left the seed. She didn’t ask why, just sat with me, her hand on my back. But I couldn’t tell her the truth: that after I placed the seed, Larkspur had changed. Her voice had turned rusty, like hinges that had been unused for decades. She started telling me stories I didn’t want to hear—about a girl who had been sealed in the walls a hundred years ago, bricked up with her hands full of mustard seeds, and who had been waiting for someone to ‘unmake the mortar.’ When I tried to leave, the fluorescent tube buzzed and died, and in the darkness I heard her laugh—a wet, crumbling sound.

I stopped going to the basement. I told Mrs. Kessler I felt sick. At home, I avoided the library books, but at night Larkspur came to my bedroom, her outline flickering like a signal from a dying satellite. She whispered through the wall, ‘You opened the door, and I’m still hungry.’ The next morning, I found mustard seedlings sprouting from the grout between the kitchen tiles, and the hum had started in my own bones.

I returned to the library, unsure of what I’d find. In the basement, the crack where I’d placed the seed had widened, and the walls were alive with pale, branching roots. And there, at the end of the corridor, stood Larkspur—only now her face was a mosaic of brick dust and mortar, and her hands were fused, fingerless, like a plant. ‘Thank you,’ she said, and her voice was the sound of a building settling. ‘Now you can be my door.’ I ran, but the hum followed me. It lives in my marrow now, and whenever I feel alone, I hear it, and I know she is still there, waiting for me to turn to page 47 again.