Shortlisted for the Hearst Big Books Award, 2019.Sometimes a promise becomes a prison.Fearing eternal singledom, childhood friends Kate and Paul make the age-old vow that if they don't find love by thirty, they will marry each other.Years later, with the deadline of their 30th birthdays approaching, the unlikely couple decide to keep their teenage promise. After all, they are such good friends. Surely that's enough to make a marriage?Now, on the eve of their 10th wedding anniversary, they will discover that love between men and women is more complex, and more precarious, than they could ever have imagined. As Kate struggles with a secret that reaches far into their past, will the couple's vo