Derek Brockway returns with a new series of rambles around Wales. Tonight he heads to mid-Wales and the spectacular scenery of Devil's Bridge and the Rheidol valley. He's joined by Lisa Jenkins, who trained here for a walk to Everest base camp, and she puts Derek through some punishing hill climbs. For the second walk Derek goes south to Margam Castle near Port Talbot. Showing him round is James Cowan, who has a special interest in the supernatural tales connected to the castle.