Iolo Williams explores the borderlands of the old county of Radnorshire. He begins his journey along the banks of the Wye between Hay-on-Wye and Glasbury, where he discovers nesting little-ringed plovers and oystercatchers. Further upriver at Llyswen, he finds spawning sea lampreys - extraordinary metre-long jawless fish.In woodlands below the Black Mountains, he comes up close with a dormouse among the ancient oak trees which began life during the reign of Elizabeth I. On Stanner Rocks near Kington, he walks on some of the oldest rocks in Wales and discovers rare plants including one that grows nowhere else in Britain. Iolo also looks for roe deer in the Radnor Forest and yellowhammers on Offa's Dyke.