Most of us spend our whole lives searching for the one. Some of us are lucky enough to find them, even for a moment. And some-like Simone and Tom-were lucky enough to find love, purchase a second home abroad, create a successful business, and build a life together for nearly four decades. But what happens after the love story?

Told through a series of notes and emails, Tom shares his raw, humorous, and heartfelt declarations on what it's like living, loving, and losing the one, Sim One, to a disease that no one talks about: cerebral amyloid angiopathy. Sim One is a love letter meets memoir that asks what does it mean to love-and keep loving-when faced with the possibility of losing it all?