When out-of-control weather brings danger to his home town, Charlie Challinor suspects that more than climate change might be to blame. Heading back to Fargone with Cadno the firefox, Lippy and Roo, Charlie discovers the magical realm is also in dire peril.

The sinister giant Gawr has stolen the Cariad, the Heart of Fargone, mixing up the world's magic and plunging the land into chaos. With the Cariad's ancient guardian, the sunlion Llew, missing in action, only Charlie and his friends can save the day - but at what cost . . . ?