Edgar is a 14-year-old boy born with mutism who communicates using a personalized sign language. He possesses a profound, almost telepathic connection with the highly intelligent dogs his family breeds in rural Wisconsin. Following the sudden death of his father, Edgar experiences intense grief and develops sharp suspicions regarding his uncle's motives. He relies on his intellect and his bond with the dogs to seek the truth about his family.

Claude is Gar's estranged brother who returns to the rural Wisconsin farm. Charismatic on the surface, he harbors a cold, calculating ambition and a deep-seated jealousy of his brother's success. Claude views the family's carefully bred dogs merely as commodities for profit. He systematically works to claim his brother's business and wife for himself.

Trudy is Gar's wife and Edgar's mother, shaped by a practical mindset developed during her youth in the foster care system. She works exhaustingly long hours to maintain the massive dog breeding operation. Following her husband's sudden death, she prioritizes the survival of the farm over her son's emotional warnings, turning to her brother-in-law for stability.

Gar is Edgar's father and the dedicated steward of the Sawtelle kennel. He approaches dog breeding as a noble science, aiming to raise canines capable of independent, moral choices. His quiet, organized leadership forms the foundation of his family's happiness until his sudden death leaves the farm vulnerable.

Almondine is the Sawtelle family's senior dog, representing the peak of the kennel's focus on canine intelligence. She possesses complex thoughts and a deep emotional capacity. She senses Edgar's mutism before his parents do and establishes herself as his lifelong, silent guardian.

Dr. Papineau is the local veterinarian who provides essential medical care for the Sawtelle kennels. He is a practical, well-meaning fixture in the rural community who tries to support Trudy after she is widowed.

Glen serves as the local sheriff in the town near the Sawtelle farm. Tasked with maintaining order, he attempts to conduct official duties but easily falls under the influence of stronger personalities in the community.

Henry is a recent widower living in a nearby town who spends his time clearing clutter from his home and listening to classical music. Having survived a broken engagement, he lives a quiet, lonely life but maintains a deeply generous spirit toward strangers.

John is Gar and Claude's father, who founded the family's dog breeding business. Inspired by the science of genetics, he dreamed of creating a superior breed of dog capable of independent, logical thought.

Violet is Edgar's grandmother. She helped establish the Sawtelle farm and raised the two deeply opposed brothers, Gar and Claude, forming the foundation of the family's complex history.

Ida runs a small grocery store in the tiny nearby town of Popcorn Corners. She is a friendly, observant neighbor who provides a sense of community connection for the isolated farm family.

Louisa is a local resident who advises Gar and Trudy on how to approach their son's lack of speech. She encourages them to learn sign language, altering the course of Edgar's life.

Forte is a massive, purebred German Shepherd who appears on the Sawtelle property as a wild stray. He shares a name with a formidable dog from Gar's teenage years, maintaining an elusive distance from the humans.

Iris is one of the breeding dogs at the Sawtelle kennel. Her pregnancy provides Edgar with his first opportunity to independently raise and train a litter.

Tinder is one of the yearling pups raised entirely under Edgar's guidance. The dog is fiercely loyal but physically vulnerable when exposed to the harsh realities outside the protected kennel environment.

Essay is a highly trusted canine in the Sawtelle pack, demonstrating the peak logic and problem-solving capabilities intended by the family's breeding program.

Benson is a wealthy businessman from Texas interested in buying Sawtelle dogs. He proposes setting up a franchise near San Antonio, representing the commercialization of the family's artistic breeding methods.

Albert is a New Jersey dog breeder who corresponded with Edgar's grandfather decades prior. He represents the skepticism of the broader breeding community toward the Sawtelles' idealistic goals.