Catriona Sinclair and her husband, James, have been struggling to have a baby. They succeed at last through in vitro fertilization but decide to make their "spare" frozen embryo available to another family, unwilling to risk the heartbreak of another miscarriage. Diana and Liam Simmons are overjoyed to learn that they are the recipients of the embryo donation. As Diana is finding delight in every aspect of motherhood, Catriona slips into a deep depression. Just as she begins to find her way back to normalcy, one of the babies is kidnapped. Suddenly, all of their lives begin to unravel and intertwine, and none of them will ever be the same.