Cosimo, a young Italian nobleman of the eighteenth century, rebels against parental authority by climbing into the trees and remaining there for the rest of his life. He adapts efficiently to an arboreal existence - hunts, sows crops, plays games with earth-bound friends, fights forest fires, solves engineering problems, and even manages to have love affairs. From his place in the trees, Cosimo sees the age of Voltaire pass by and a new century dawn.