Fone Bone, Phoney Bone, and Smiley Bone are run out of their home, Boneville, and become separated in the wilds, but better fortune begins when Fone meets a young girl named Thorn.
Fone Bone and Thorn, trapped in a dungeon, manage to escape and join Thorn's grandmother in a battle against the rat creatures before leaving on a quest to find the Crown of Thorns and end the war.
Princess Rose musters up courage to face the dragon that threatens the small towns in the Northern Valley, only to discover the dragon is actually the Lord of the Locusts; and meanwhile, her sister, Princess Briar, embarks on a more sinister quest.
Phoney Bone rigs the Spring Fair's annual Great Cow Race by putting Smiley in a bovine disguise and convincing everyone to bet their livestock on the mystery cow, and Fone Bone finds himself in a one-cousin battle with the rat creatures.
Fone Bone and Smiley return a lost rat creature cub to the mountains and discover Rock Jaw, a giant mountain lion whose big ambitions bring him face-to-face with monstrous competition.
Lucius, Smiley and Phoney are attacked by rat creatures in the forest, barely making it to Lucius' tavern, while, at the farm, Fone Bone and Thorn are having strange dreams and Gran'ma Ben suddenly begins revealing secrets and new dangers.
After stepping into a ghost circle Thorn is urged to locate the Crown of Horns, and sets off on a quest with Fone Bone to traipse through the sacred grounds of dragons, with the hope of returning with the only thing that can save everyone and everything she holds dear.
