The series followed the adventures of Roger Beckett (aged 10¾) in Troller's Ghyll ("where the rocks are all slightly mad") as King of the Rottentrolls. He was crowned King of the Rotten Trolls after crashing his bike in the valley. As well as ruling over the Rottentrolls, Roger teaches them about things like sport and politics, and, in return, learns a few lessons himself.