County Sheriff Rube Whitlock is faced with raising his two young sons after the death of his young daughter which leaves his wife mentally incapacitated with grief and unable to care for them. Overwhelmed with the responsibility, Rube hires Esther, a local black woman whose husband, PV has just purchased his second mule in an attempt to establish himself and his farm as competitive cotton producers. Word of PV’s ambition quickly spreads through town igniting the community’s rage, creating dissonance and contempt within the usually quiet community.

Tensions rise as Orville “Guppy” Walters, a local ne’er-do-well, instigates a campaign that begins to threaten the safety of PV. These rumblings put Rube’s loyalties and the stability of his position as sheriff under scrutiny and it begins to compromise his livelihood.

As the condition of Rube’s wife deteriorates, Esther’s natural maternal presence begins to fill voids in the Whitlock house, which further fans the racial fires in the town. Rube is ultimately forced to choose between the boundaries set by the laws he has sworn to uphold and the boundaries set by the moral convictions of the human heart.

Amidst painful pasts beginning to resurface and new secrets freshly buried, it will take a “knobby-kneed buckskin” mule, a cheap pocket knife and a lifeless Cottonwood tree to form lasting friendships that will gray the lines between black and white and begin the delicate mending of family ties in the tender heart of a young boy.