Based on a true story spanning over 15 years, Decoding Annie Parker follows Parker, a brave and irreverent woman who watches her family stalked and devastated by the cruel disease, Meanwhile, geneticist Mary Claire King begins researching the idea that there is a genetic link to the type of cancer that afflicts people like Annie, though few give credence to her ideas. As the years pass, the cancer also comes for Annie, and it changes not only her body, but her relationship with her husband and her son who are both ill-equipped to deal with the mayhem that descends upon them. As Annie rises up and fights against the odds, Dr. King manages to find something of unimaginable significance.