Bartemus and friends are back at it in the second installment of the Prairie Adventure series. When Grandfather is called to the Back of the Giants, the huge mountains on the western edge of the Sea of Big Grass, Bartemus doesn't think too much about it. After all, Grandfather can take care of himself, right? When Grandfather doesn't return, and a strange visitor demands that Bartemus come to the mountains, Bartemus and his friends have to risk fur and feather traveling across the Prairie. They overcome wild fires, erratic Prairie Dogs, and fierce Mountain Lions (not to mention Willoughby's insatiable appetite) to make it to the Hall of the Mountain Queen, only to discover that Grandfather has more secrets to share with the Critters. Can Bartemus, Timblelew, Willoughby, Wynstan, and Simon unravel the mysteries surrounding Grandfather's disappearance, stop a civil war on the mountains, and make it back to the Hollow before it's too late?