Treading carefully around her and latching the door, my most immediate concern was providing my new customer with a sense of safety and discretion. But my fears were unwarranted, for she plopped into one of my two chairs as though she’d been at my shop a hundred times. I could see her better now that she sat in the light. Her figure was a slender one, and she had clear, hazel eyes, almost too large for her oval-shaped face. Intertwining her fingers and setting her hands on the table, she looked at me and smiled. “Hello.”

“Hello,” I replied, surprised by her manner. In an instant, I felt a fool for having sensed any doom in the blush-colored letter written by this child. I wondered, too, about her beautiful penmanship at such a young age. As my sense of worry diminished, it was replaced with a relaxed curiosity; I desired to know more of the girl.

I turned to the hearth, which claimed one corner of the room. The pot of water that I had set over the fire a short time ago spewed entrails of steam. “I’ve hot-brewed some leaves,” I said to the girl. I filled two mugs with the brew and set one of them in front of her.

She thanked me and pulled her mug toward her. Her gaze came to settle on the table, on which rested our mugs, a single lit candle, my register and the letter she’d left in the bin of pearl barley: For my mistress’s husband, with his breakfast. Daybreak, 4 Feb. The girl’s cheeks, pink upon her arrival, remained flushed with youth, life. “What kind of leaves?”

“Valerian,” I told her, “spiced with cinnamon bark. A few sips to warm the body, a few more to brighten and relax the mind.”

We were quiet, then, for a minute or so, but it was not uncomfortable in the way that it can be between adults. I supposed the girl to be grateful, foremost, to be out of the cold. I gave her a few moments to warm herself, while I went to my counter and busied myself with a few small black stones. They needed smoothing along the grinding board, after which they would make ideal vial stoppers. Aware of the girl watching me, I lifted the first stone and, pressing down with my palm, rolled it, spun it around and rolled it again. Ten or fifteen seconds was all I could manage before I had to stop and slow my breath.

A year ago, I was stronger, and my strength was such that I could roll and smooth these stones in a matter of minutes, without so much as brushing a hair from my face. But on this day, with the child watching me, I could not go on—my shoulder ached too badly. Oh, how I did not understand this ailment; months ago it had been borne in my elbow, and then shifted into the opposite wrist, and only very recently, the heat had begun to slip into the joints of my fingers.

The girl remained still, her fingers wrapped tightly around her mug. “What’s that bowl of creamy stuff, over there by the fire?”

I turned away from the stones to look at the hearth. “A salve,” I said, “of hog’s lard and purple foxglove.”

“You’re warming it, then, for it’s too hard.”

I paused at her quick understanding. “Yes, that’s right.”

“What is the salve for?”

Heat rose in my face. I could not tell her that the leaves of purple foxglove, when dried and crushed, sucked the heat and blood from the skin, and therefore assisted a great deal in the days after a woman had birthed a child—an experience unknown to girls the age of this one. “It is for a tear in the skin,” I offered, taking a seat.

“Oh, a poisonous salve for a tear in the skin?”

Shaking my head, I said, “No poison in this, child.”

Her little shoulders tensed. “But Mrs. Amwell—my mistress—told me you sell poison.”

“I do, but poison is not all I sell. The women who have been here for deadly remedies have seen the extent of my shelves, and some have whispered of it to their most trusted friends. I dispense all sorts of oils and tinctures and draughts—anything an honorable apothecary might require in her shop.”

Indeed, when I began dispensing poisons many years ago, I did not simply clear my shelves of all but arsenic and opium. I continued to keep the ingredients needed to remedy most afflictions, supplies as benign as clary or tamarisk. Just because a woman has rid herself of one malady—a devious husband, for instance—does not mean she is immune to all other maladies. My register was proof of it; interspersed among the deadly tonics were also many healing ones.

“And only girls come here,” the child said.

“Did your mistress tell you that, too?”

“Yes’m.”

“Well, she was not mistaken. Only girls come here.” With the exception of one long ago, no man had ever stepped foot in my shop of poisons. I only aided women.

My mother had held tight to this principle, instilling in me from an early age the importance of providing a safe haven—a place of healing—for women. London grants little to women in need of tender care; instead, it crawls with gentlemen’s doctors, each as unprincipled and corrupt as the next. My mother committed to giving women a place of refuge, a place where they might be vulnerable and forthcoming about their ailments without the lascivious appraisal of a man.

The ideals of gentlemen’s medicine did not align with my mother’s, either. She believed in the proven remedies of the sweet, fertile earth, not the schemes diagrammed in books and studied by bespectacled gentlemen with brandy on their tongues.

The young girl in my shop looked around, the light of the flame in her eyes. “How clever. I like this place, though it is a bit dark. How do you know when it is morning? There are no windows.”