Little Willy is a ten-year-old boy tasked with running a Wyoming potato farm after his grandfather unexpectedly falls ill. Young but exceptionally responsible, he shoulders the burden of the farm's harvest and financial troubles. He loves his grandfather and his dog deeply, displaying an innocence and determination that drives him to find a way to pay off the farm's sudden debts by entering a dangerous sled race.

Grandfather is a kindly older man who has raised his grandson, Little Willy, since the boy's mother died. Normally a cheerful prankster who works hard on their potato farm, he falls into a severe depression and refuses to speak or leave his bed. His sudden passivity leaves the fate of their family farm entirely in his young grandson's hands.

Stone Fox is an imposing and highly skilled Indigenous sled racer of the Shoshone tribe who has never lost a race. He maintains a strict vow of silence toward white people as a protest against the historical mistreatment and displacement of his people. He uses prize money from sled races to quietly purchase back land for his tribe.

Searchlight is a loyal black dog born on the exact same day as her owner, bearing a distinctive white spot on her forehead the size of a silver dollar. She shares a nearly telepathic bond with Little Willy. She eagerly helps with heavy farm chores like pulling the plow, serving as the boy's constant companion and protector.

Mr. Clifford Snyder is a tax collector for the state of Wyoming. Short in stature with a thin mustache, he is deeply afraid of dogs and readily points a weapon at Searchlight. He brings the harsh reality of a massive unpaid tax bill to the farm, demanding immediate payment.

Doc Smith is an elderly town doctor with snow-white hair and a heavily wrinkled face. She is a pragmatic medical professional who quickly diagnoses Grandfather's ailment as a loss of the will to live. Though she frequently advises Little Willy to give up the farm and move in with her, she genuinely cares for the boy's well-being.

Mr. Foster is the president of the local bank. He is a practical, business-minded man who views the farm's financial situation objectively. When Little Willy seeks help with the tax debt, Mr. Foster strongly advises the boy to sell the farm rather than risk his college fund on a race.

Lester is the kind-hearted proprietor of the local general store. He provides Little Willy with supplies and information, showing sympathy for the boy's difficult situation and offering him details about the upcoming dogsled race.

Mayor Smiley is the leader of the town who oversees the National Dogsled Races. He attempts to discourage a ten-year-old from entering such a dangerous competition but ultimately accepts the registration fee and starts the event.

Dusty is the town drunk who spends time at Lester's store. He is primarily responsible for spreading wild rumors about Stone Fox's strength and alleged violence, contributing to the town's fear of the Indigenous racer.