Sisters Venus and Serena Williams are two of the most successful tennis players of all time. They've provoked strong reactions - from awe and admiration to suspicion and resentment. They've been winning championships for over a decade, pushing the limits of longevity in such a demanding sport. How long can they last? Following their extraordinary story - from young black girls from the ghetto training with their father to international stardom - this film features unprecedented access into their lives during the most intimidating year of their careers. Over the course of 2011, Venus grappled with an energy-sapping autoimmune disease while Serena battled back from a life-threatening pulmonary embolism. Now, as they prepare for this year's Wimbledon, this is a unique insight into two sisters who do not let their adversities hold them back, drawing their strength from each other.