Derek and the team travel to the point where the counties of Carmarthenshire, Pembrokeshire and Ceredigion all meet to follow the course of the River Teifi between Cenarth and Cilgerran. On the way he learns to steer a coracle, the area's ancient form of fishing boat. At when he reaches Cilgerran he takes part in the annual coracle races. Meanwhile Matt Bassett visits possibly the prettiest producers' market on the Teifi Estuary and Dr Jeni Millard discovers the story of Wales' smallest museum.

'Derek the Weatherman' hopes it will be warm when he takes part in the World Bog Snorkelling Championships in mid Wales. It's at the end of his walk that follows part of the trail along the Heart of Wales Railway, starting in Llandovery. On his way he takes part in a tug-of-war with young farmers and has afternoon tea under and impressive railway viaduct. Matthew Bassett joins cyclists in Llandovery and wildlife expert Lizzie Daly goes in search of pied flycatchers in rare Atlantic oak woodland.