Fone Bone and Smiley Bone strike out into the wilderness to return a lost Rat Creature cub to the mountains. It doesn't take long before they run smack into Rock Jaw, a sly and mighty mountain lion with a none-too-friendly disposition. Life gets even more complicated when they befriend a group of baby animals who have been orphaned by Rat Creature attacks. Everything comes to a head in an earth-shattering clash between Rock Jaw and Kingdok, the leader of the Rat Creatures.