Every summer, Belly (short for Isabel) travels to the beach house with her mom and brother to spend time with her mom's best friend, Susannah, and Susannah's two sons, Conrad and Jeremiah. This summer is different—Belly is fifteen, and for the first time, the boys seem to notice she's not just a little kid anymore. As she navigates her changing relationships, first love, and family secrets, Belly learns that growing up means facing difficult truths and making hard choices.