'Una - the One' is a powerful documentary about the 'holy river' of Bosnia-Herzogovina, the Una. This river, which the Romans found so beautiful that they named it 'The One', is home to a remarkable diversity of habitats, and an equally large diversity of fish species, including brown trout, grayling and hucho, also known as the danube salmon. These fish, which are more or less unique to the region, can grow to astonishing sizes and present a challenge to any fly angler. But like many rivers in Europe, the shadow of a proposed damming project, which would dramatically alter the river's flow, looms large, and with this one of the last unadulterated hucho habitats in the world is under threat. Can a group of passionate anglers save the river from irreparable damage?