Clare Balding heads for the Clwyd Hills in North Wales as she joins the county's Archaeologist, Fiona Gale, to find out more about the many Iron Age hill forts that are so prevalent along the range. They start at Moel Arthur , walking along to Penycloddiau, one of the largest sites. They are joined by two of Fiona's colleagues. David Shiel and Helen Mrowiec, all three of whom are passionate about the area and the leisure opportunities it offers. While they all discuss the marks left on the landscape by past generations, Clare and her companions become united in their hatred of a twenty first century scar, the plastic dog poo bag, filled and left hanging on branches or in bushes. Clare is now on a mission to eradicate these eyesores from the countryside.