Loosely based around the true story of a fur trapper-turned-Oregon Trail guide who led a group of settlers on an ill-advised short cut, Kelly Reichardt’s latest is not just the strongest work of her career, but one of the best films you’re likely to see all year, a quiet, meditative masterpiece that examines the cultural and gender norms of the United States in the 19th century within the context of a life-or-death struggle for survival.