Richard travels to Scotland to journey down the River Clyde and learn about its environmental importance. This wild and powerful waterway is also going through huge environmental changes. From its mouth, Richard goes in search of clawed alien invertebrates who have taken over the upper stretches of the river, decimating wildlife. He sees how the wildness of this river has been harnessed by people to create power, and further downstream he learns about the impact the Clyde has had globally