But as they step into the unfamiliar realm of sisterhood, the roles will reverse in ways no one could have foreseen. Caroline lives a full, happy life - thriving career, three feisty children, enviable marriage, and a close-knit extended family. She couldn't have scripted it better. Except for one thing: She's about to discover her fundamental beliefs about them all are wrong. Sela lives a life in shades of gray, suffering from irreversible kidney failure. Her marriage crumbled in the wake of her illness. Her beloved mother, always her closest friend, unexpectedly passed away. She refuses to be defined by her grief, but still, she worries what will happen to her two-year-old son if she doesn't find a donor match in time. She's the only one who knows Caroline is her half sister and may also be her best hope for a future. But Sela's world isn't as clear-cut as it appears - and one misstep could destroy it all.