Eleven-year-old Annie Parker is living the perfect young life, loved by all, and especially by her mother, father, and older sister. But none of them knows that something horrible is stalking their perfect family. On a fall afternoon in 1976, young Annie hears a noise from upstairs. Her mother has collapsed and died, and an agonizing downward spiral begins. At U.C. Berkeley, a brilliant research geneticist named Mary-Claire King (Helen Hunt) is embarking on something of a personal crusade to uncover the genetic roots of breast cancer. While still in her twenties, she has already made a famous discovery that made the cover of the prestigious journal Science -- quantifying the genetic variation between humans and chimpanzees. But her conviction that there is a hereditary basis to at least some forms of breast cancer is not widely shared. Nevertheless, her tireless research throughout the 1980's would end in a medical breakthrough -- the discovery of the location of the BRCA1 hereditary breast cancer gene --- considered one of the most important scientific discoveries of the twentieth century. At the age of 19, after the sudden death of her father, Anne (Jade Duncan) marries Paul (Aaron Paul) and soon is pregnant. She struggles to find a way in the world with her equally young but misguided husband and her older sister, Joan Parker (Marley Shelton) who tries to become a surrogate parent to Anne. But, cruelly, Joan contracts the same cancer that killed their mother, and in a few months, she, too, is dead. Annie (Samantha Morton) is diagnosed with the same disease that killed her mother and sister -- breast cancer. It is severe, and surgery and chemotherapy, with all the accompanying difficulties, soon follow. She loses her hair, and if that wasn't enough to endure, her husband, never really mature or stable, has begun an affair with Anne's closest friend Louise (Alice Eve), and leaves her. Paul is soon diagnosed with cancer and expires shortly before she is diagnosed with a second cancer. While Annie struggles, King is pursuing her belief that some forms of breast and ovarian cancer have a hereditary basis. While she captures headlines for her work applying DNA fingerprinting to help reunite "the disappeared" with their families in Argentina, her priority is to map the breast cancer gene. King focuses on collecting families with a particularly high incidence of breast cancer, suspecting that these cases are most likely to reveal any genetic predispositions. Advances in genetic mapping through the 1980's gradually allow her team to embark on studies to map the location of the BRCA1 gene. Finally, in 1990, King and her team find conclusive evidence linking DNA markers on chromosome 17 with an inherited flaw in a gene dubbed BRCA1. The work was presented at the American Society of Human Genetics conference in Cincinnati, and published in Science a short time later. Mary Claire King ended up on the cover of Time, and Anne Parker finally had the answer she herself had long sought. Anne Parker happily remarried (Bradley Whitford), and a few years later contracts cancer for a third time. And survives again. And she laughed while being treated, for reasons only she knew and understood.