Lost in the mysterious woods of the Unknown, two brothers named Wirt and Gregory run into a jaded old woodsman who warns them to beware the terrifying Beast that roams the dark forest.

A bluebird named Beatrice offers to guide Wirt and Greg to Adelaide of the Pasture (the good woman of the woods) and help them get home.

Wirt, Greg, and Beatrice get all mixed up in the musical antics of a schoolhouse of animals, a lovelorn teacher, a grouchy old benefactor, and an escaped gorilla.

Beatrice is left out in the rain with a brainless horse while Wirt and Greg must ask for directions in a lively colonial tavern called "The Dark Lantern" where some surprising secrets are revealed about the Unknown.

Is millionaire Quincy Endicott's sprawling mansion haunted by a beautiful ghost, or is the tea baron going mad? Greg and Fred the Horse are on the case! Meanwhile, Wirt and Beatrice get trapped in an armoire while searching for loose change.

We join Wirt and Greg on a lighthearted romp aboard the Frogland Ferry as they approach Adelaide of the Pasture. But why is Beatrice acting so glum? Things turn emotional for Greg as well when he realizes that his own frog may be better off living with his amphibian compatriots.

After unexpected darkness tears the gang apart, Wirt takes charge and meets Loma, a young woman forced to do housework by an odious witch with a magic bell. Can Wirt and Greg save Lorna, and themselves, from the wicked witch?

While Wirt and Greg lay down to rest, they're drawn into a dreamworld of cherubs, flowers, and clouds where Greg must battle the North Wind.

The Beast has come. The final chapter begins.