Single mother Kate O'Hara's daughter, Rosie, is one of a small percentage of children with a disorder that prevents them from being immunized. All Kate can do is hope that herd immunity keeps disease at bay and her little girl safe. Madeleine Cooper and her husband declined measles shots for their daughter Clara; vaccinations were a leap of faith she wasn't prepared to take. Then both girls wind up in the same elementary school class, and both girls get sick. Will Kate pay for Madeline's choice?