Writer and angler Will Millard begins his journey down the River Wye in the wild mountains of mid-Wales. He goes in search of the river's source on the slopes of Plynlimon, before learning how a local sheep farmer has diversified by turning some of his land into a destination for petrolheads. He explores how a legacy of heavy industry polluted the entire Wye catchment, acidifying its waters and damaging the ecosystem. Now an environmental charity is working hard to right the wrongs of the past with some basic chemistry and some heavy machinery. The way rivers are viewed is changing and Will takes a detour off the main river up one of its tributaries to reflect on the benefits of being immersed in nature. After spending a night in the wilds, Will explores how the waters that feed the Wye have been harnessed as a valuable natural resource. The upper reaches of the River Wye is also an important sanctuary for a diverse range of wildlife, but what we see today is just a fraction of what the river must once have been and could be once more. Will goes in search of a river-dwelling animal that hasn't been seen on a Welsh river for centuries. As an obsessive angler, Will couldn't make a journey down the Wye without trying to hook a fish or two. He's never caught Wye salmon, the river's most iconic species, but it's not going to be easy.