This Grand Tour begins in the hills above Glen Clova, on a mountainous plateau known as The Mounth. Following the South Esk downstream, Paul enters picturesque Corrie Fee, where he scrambles on the cliffs with two botanists, searching for Scotland's rarest plant. Back on the South Esk, Paul goes electro-fishing to discover more about the ecology and general health of the whole river system. Running out of riverside paths, Paul takes to the road for a few miles and rides a motorbike to the ancestral home of Harley Davidson. He later discovers how social distancing in the 17th century enabled traders to ply their wares during the plague in Brechin, Scotland's smallest city. Where the river enters the salt-water Montrose Basin, Paul learns how plans to transform the tidal basin into a Dutch-style polder for agriculture were scuppered by a storm witch — or was she just a scapegoat for competing interests? During the Second World War, the Norwegian Navy was stationed in Montrose. Their mascot — a huge St Bernard dog called Bamse — became a war hero and national celebrity. Paul pays homage to the giant dog with a visit to his statue, before visiting a lighthouse standing guard over the rocks of Scurdie Ness. The final river in this series is the Ayr, which Paul follows as it flows from Loch Glenbuck towards the sea and the Clyde coast. The old mining village of Glenbuck was demolished long ago, but its memory is being kept alive by former resident Barbara Alexander, whose uncle — legendary Liverpool football manager Bill Shankly — was a Glenbuck man. From Glenbuck, Paul follows the river through a landscape pockmarked by the scars of old mineral extraction and industry. At Muirkirk he discovers how a local man illuminated the cities of the world with gas lighting, and how a certain Mr McAdam invented tarmac for the roads of the world. The course of the River Ayr flows through land rich in covenanting history, when religious conflict cost many lives. At the Ayr Gorge, Paul encounters the extraordinary tale of radical preacher Alexander Peden, whose life on the run forced him to hide in caves while still preaching hell-fire sermons to the people. Finally reaching the coast, Paul visits the only working salt evaporation tower in the world, where he learns how sea water is evaporated by wind and sun to make brine, from which sea salt is made.