Throughout the series of books (there are currently three complete novels with plans for nine books total), Bartemus and his best friends must battle evil forces that would take over the Prairie and all the Critters who live there. Grandfather often helps, but it is through their friendship, love for the Prairie, love for music, and their general penchant for getting into trouble that keeps the Critter gang in more adventure than they can handle.

Bartemus Ammblin is in his eighth year at the Burrowton School when events change his normally mundane life. When the Hollow Faire is interrupted by a mysterious stranger and Wolves attack the Hollow, Bartemus and his best friends must band together to save their families.

In this first volume, the mystery behind Grandfather and all his wonderful, mystical powers is first generated. The topography and social structure of life on the Prairie is developed. The first adventure, involving the renegade Dire Wolf Nihilus, is undertaken by Bartemus and company. The extinction of the Giant Sloth and the destruction of the Dire Wolf hearken to warnings of the coming "plague that walks on two legs."

Bartemus and friends have to cover for Grandfather when he is suddenly called to the Back of the Giants - the mountains that form the western border of the Prairie. Something or someone is keeping the rain from the Prairie and the Hollow is beginning to run dry. Bartemus receives word that he is needed and races to join Grandfather. The Critters find themselves caught between the forces of Dessina, the Mountain Lion, and Bantama, the Thunderbird. When Grandfather is taken prisoner and a dark stranger is found aiding Bantama with powerful magic, Bartemus and friends are forced to join in the battle or risk being destroyed!

A strange creature, never before seen on the Prairie, arrives from the northwest and causes panic in Queen Bariana's realm. This huge, lumbering Critter is dumb-founded and has lost its ability to communicate. Using this poor Critter as his rallying point, Thaebos the Wise, a seer, makes the Critters of the Northern Prairie believe that the world will end unless they follow his lead. Fearing an apocolypse, the Prairie Dogs, led by Generalissimo Paisano (introduced in volume 2), band together to form a Grand Army of the Prairie. Spurred on by the fanatical Bear Thaebos, the Prairie Dogs are bent on taking over the Sea of Big Grass.

Back in the Hollow, Willoughby gets ready for the annual Hollow Faire by designing his own carnival ride. When all of the local Prairie Critters arrive for the festival, a group of fanatical Birds, led by a vengeful Owl, lead a separatist movement dividing Nestings from Burrowton. These radicals from the Southern Prairie, known as Avians, will not stop until the Bird way of life is established on the Prairie.

Bartemus and his friends must sort through the clues that led up to the rise of the Bear in the North and the Birds in the South and try and stop both groups from tearing apart Prairie society before its too late.

Bartemus begins to notice that his magical abilities are harder to control as he's noticing girls for the first time. It's an awkward situation, but when he travels to P.A.W.S for a visit, it's made worse when he's captured by a crazed band of Ground Squirrels! Led by the dashing Commander Alexander, the Pyrates of the Tallgrass Prairie kidknap Bartemus and force him to locate a buried treasure. Only Willoughby, Wynstan, Timblelew and Simon can save Bartemus from the clutches of these dastardly Critters and unravel the secret of the Treasure of the Tallgrass Prairie.