This is the account of Tom Bullough’s journey along Sarn Helen – Helen’s Causeway – the old Roman Road that runs from the south of Wales to the north. As Bullough walks the route, he explores the political, cultural and mythical history of this small country that has been divided by language and geography. Woven into this journey are conversations with climate scientists and the story of Tom’s engagement with the urgent issue of the climate crisis, showing us its likely impact on Wales, which is – in miniature – a vision of what lies ahead for us all.