Who, or what, is the Green Man, and why is this medieval image so present in our precarious modern times?

An encounter with a carving of the Green Man at an ancient church leads Nina Lyon on a search to track him down in all his various guises. Against a backdrop of mountains, forests, rivers and stone circles, a cult of the Green Man emerges, as Nina explores his meaning and how he came into being. Meanwhile, in the woods, from an overgrown Welsh railway line to leafy London suburbia, strange things are happening . . .