In 2010, filmmaker Lucy Walker brought to Mountainfilm the unforgettable story of Vik Muniz, the Brazilian artist in Waste Land. In 2011, she captured the personal impact of the tsunami in Japan (The Tsunami and the Cherry Blossom). And last year, she screened The Crash Reel, which shows the uphill struggle of snowboarder Kevin Pearce as he recovers from a traumatic brain injury. This year, Walker is back with her lens trained on Marianna Palka, an appealing young woman on the verge of finding out whether or not she has Huntington’s disease, which has symptoms much like a brutal mix of Parkinson’s and Alzheimer’s. Walker’s access and sensitivity to her subject is remarkable — as is the resulting film.