"If there are infinite worlds, every version of me chooses you in every one of them." - Belly How true can these words be when time itself decides to test them? At twenty-four, Isabel "Belly" Conklin wakes to find herself fifteen again-back at Cousins Beach, on the edge of the summer that changed everything. She remembers it all: the years with Jeremiah that ended in heartbreak, the slow and certain love that grew between her and Conrad, and the inconceivable ache of losing Susannah, whose presence had shaped all their lives. But now, with the impossible circumstance of reliving it, Belly believes she's been given a purpose: to protect her future with Conrad, to rewrite the choices that once broke them, and to make this last summer with Susannah count in every way that matters. Only, the past begins to shift, and bend into something unrecognizable. And as the tides of Cousins pull her between what was and what should be, Belly starts to wonder- if the future she remembers is as guaranteed as she wants to believe.