One October afternoon three years ago while I was visiting my parents, my mother made a request I dreaded and longed to fulfill. She had just poured me a cup of Earl Grey from her Japanese iron teapot, shaped like a little pumpkin; outside, two cardinals splashed in the birdbath in the weak Connecticut sunlight. Her white hair was gathered at the nape of her neck, and her voice was low. “Please help me get Jeff’s pacemaker turned off,” she said, using my father’s first name. I nodded, and my heart knocked.

Upstairs, my 85-year-old father, Jeffrey, a retired Wesleyan University professor who suffered from dementia, lay napping in what was once their shared bedroom. Sewn into a hump of skin and muscle below his right clavicle was the pacemaker that helped his heart outlive his brain. The size of a pocket watch, it had kept his heart beating rhythmically for nearly five years. Its battery was expected to last five more.

After tea, I knew, my mother would help him from his narrow bed with its mattress encased in waterproof plastic. She would take him to the toilet, change his diaper and lead him tottering to the couch, where he would sit mutely for hours, pretending to read Joyce Carol Oates, the book falling in his lap as he stared out the window.

I don’t like describing what dementia did to my father—and indirectly to my mother—without telling you first that my parents loved each other, and I loved them. That my mother, Valerie, could stain a deck and sew…