Dearest heart, gut, and nervous system, Simply because we're riding down the Carolina Coastal Highway with Zac doesn't mean we're on some romantic trajectory. Just sayin'. Yours, forever biologically linked, Grace Callahan. Grace's life is one surprising roadside stop after another. Her dad is getting remarried. Her estranged (emphasis on strange) sister declares they're going to the wedding via a road trip. And Zac, the guy next door, her forever friend and boyfriend, breaks up with her then doesn't say a word to her for fifty-nine days, nineteen hours, and thirty-six minutes. In fact, the closest Grace got to communicating with him was the secret notebook she kept, the one that started with Dear Zac and ended as the weirdest love letter of all time (weather reports included). But when her sister bails on their trip, Zac offers to join Grace. Suddenly there is more than smashed pennies and an alligator named Arlo on the itinerary, because staring down a toothy reptile at dawn is nothing compared to the biggest discovery she must make. This journey will either map the end of Grace and Zac or become a whole new beginning for them.