Maisie is still reeling from the loss of her dad when her mom deposits her with Aunt Gertie at the start of summer in Heaven, TX. Population: tiny. Gertie is nothing but nice, but Maisie doesn't want to be there - surrounded by cactus and tumbleweeds. Thankfully, the Heaven Library is well air-conditioned. Here, Charlene the librarian offers Maisie much-needed solace and book recommendations. Then Maisie meets another actual kid, Walt Wise, Aunt Gertie's nearest neighbor. As she and Walt work odd jobs together and become friends, they also stumble upon a stealth campaign to develop one of Heaven's most beloved natural resources. As Maisie and Walt research the development plan, they also uncover a long-buried, life-changing secret about Maisie's family.

This secret, along with an explosive event at the Heaven County Fair, will turn a sleepy summer into one Maisie and Walt will never forget.