Some spend their whole lives searching for “the one.” Some of us are lucky enough to find that special person, even if just for a little while. Then there are some—like Simone and Tom—who are lucky enough to find unconditional love, mutual admiration and a lifelong best friend.

Together they designed a nest in the country, with a village place abroad to honor her French father, creating a successful business together that gave them, as sought-after experts who loved travel, the rest of the planet … sharing an intense life together for nearly four decades. But what happens when a bad diagnosis suddenly threatens that love story? Told through a series of notes and emails, Tom shares his raw, wrenching account of what it’s like living, loving and losing over 18 months the one, Sim One, to a traitorous brain. Sim One is an intimate love letter meets memoir. It asks what it means to love—and keep loving—when faced with the possibility of losing it all….