But Bishop was right, and maybe right to be offended. I know now what a chilly prude I was then, believing that carnal appetites, whether women’s or men’s, were deplorable inside marriage and out. And once children arrived, I was sure, the only passion between husband and wife should be whatever reproduction required. Indulging sensual gusts, I thought, was incompatible with the duties of parenthood.

Bishop moved close enough that I could see the sweat on his upper lip, and something between hurt and cruelty in his eyes. “Your sister is mad. And the sooner we come to terms with it, the better we’ll all be. The child most of all.”

I doubted him, my sister, myself. I knew that because of my father I assumed all men to be despots until they proved otherwise. I saw no change in Bishop, no willingness to bend to her plight, to feel compassion for his wife. But was I being unfair?

I missed Fanny desperately, wrote to her every day, about the vicissitudes of Eliza’s madness, the precipice of my own. We were only in Bermondsey, but it felt a world away, and leaving Eliza, even for an afternoon, seemed dangerous. What she might do to herself, what Bishop might do to her.

One night I woke from a troubled sleep, twisted in my bedclothes. My nightmare compelled me to throw the covers off, put a robe on, tiptoe down the hallway and around the corner toward their room, without even a candle to light my way. When the floor creaked under my bare feet, I froze, until it felt safe to creep some more. When I neared their door, I heard it, what I’d heard so many nights of my youth. Him, grunting, groaning, clipped commands telling her what to do, how to lie. Her muffled shrieks, moans, sobs.

This, if not the first cause of my sister’s madness, was the fuel to its consuming fire.

“Eliza,” I said the next morning, sitting her down and kneeling at her feet. “I need you to listen, Eliza.” I took her face in my hands. “I believe you. Everything you told me.”

She put her hands over my hands, and leaned closer, sheer terror in her eyes. “I will die if you leave me here. I’m begging you, Mary.”

I tried to talk to Bishop, to suggest that he try gentleness with her, or put his own gratification to the side, at least until she regained herself.

“Of course you take her side. She’s your sister.”

“She’s a woman in pain, of course I feel for her. Why can’t you?”

“I house her, feed her, clothe her. Those are my husbandly duties! And what are hers to me?”