In the summer of 1977, Victoria Leonard's world changed forever--when Catilin Somers chose her as a friend. Dazzling, reckless Caitlin welcomed Vix into her heart of her sprawling, eccentrick family, opening doors to a world of unimaginable privilege, sweeping her away to vacations on Martha's Vineyard, a magical, wing-blown island where two friends became summer sisters....

Now, years later, Vix is working in New York City. Caitlin is getting married on the Vineyard. And the early magic of their long, complicated friendship has faded. But Catilin has begged Vix to come to her wedding, to be her maid of honor. And Vix knows that she will go--for the friend whose casual betrayals she remembers all too well. Because Vix wants to understand what happened during that last shattering summer. And, after all these hears, she needs to know why her best friend--her summer sister--still has the power to break her heart...