Lucy Houston and Mickey Chandler probably shouldn’t have fallen in love, let alone gotten married. They’re both plagued with faulty genes—he has bipolar disorder, and she has a ravaging family history of breast cancer. But when their paths cross on the night of Lucy’s twenty-first birthday, sparks fly, and there’s no denying their chemistry. Cautious every step of the way, they are determined to make their relationship work—and they put it all in writing. Mickey promises to take his medication. Lucy promises not to blame him for what is beyond his control. He promises honesty. She promises patience. Like any marriage, they have good days and bad days—and some very bad days. In dealing with their unique challenges, they make the heartbreaking decision not to have children. But when Lucy shows up for a routine physical just shy of their eleventh anniversary, she gets an impossible surprise that changes everything. Everything. Suddenly, all their rules are thrown out the window, and the two of them must redefine what love really is.