Jack is a border collie narrator seeking a meaningful life after a fire destroys his farm. Driven by a deep instinct to herd and be useful, he trusts humans implicitly, which pulls him into both comforting and dangerous situations. Throughout his travels, he experiences a variety of names and temporary homes while trying to figure out where he truly belongs.

Luke is a young orphan living at the Good Shepherd Home for Boys. Struggling with reading and suffering from low self-esteem due to his father's criminal background and his mother's absence, he feels unworthy of being adopted. He connects instantly with Jack, treating the dog as an equal and offering him mutual understanding.

The Goat Man is an itinerant traveler who lives off the land alongside his herd of goats. He embraces a transient lifestyle and carries a quiet wisdom that he shares with Jack. Dealing with old grief from the loss of his wife and infant son, he offers the dog food, shelter, and a philosophical perspective on finding contentment in the present moment.

Billy is the cruel master of Billy's Big and Happy Circus. He exploits and mistreats the animals under his control, keeping them in terrible conditions to force their performance for his profit. He views his animals purely as interchangeable property rather than living beings, punishing them severely when they refuse to obey.

Tiffany is a female dog trapped within Billy's abusive circus. Despite the grim conditions, she cultivates a strong sense of community among the captive animals and advises newcomers to obey Billy to survive. She bears her circumstances out of a deep loyalty to the other animals who rely on her strength.

The Little Girl is a young child who takes Jack in from a pet store, naming him "Baby" and pushing him around in a stroller. Though she cares for him and provides a safe environment, she treats him like an infant rather than a working dog, clashing with his inherent need to be free and useful.

The Thieves are a pair of opportunistic men who survive by stealing from crowds near the train tracks. They initially take Jack in and name him "Spot," but quickly exploit the dog by using him in a "play dead" routine to distract onlookers while they pickpocket them.

The Older Woman is a kind adult who dedicates her time to collecting clothes for those in need. Despite lacking wealth or a tidy home, she provides Luke with a willing role model and patiently helps him practice his reading skills when he visits.

The Woman In Charge runs the Good Shepherd Home for Boys. She maintains strict rules at the orphanage, immediately throwing Jack out when she finds that Luke smuggled him inside for the night.

The Perfect Parents are a couple visiting the Good Shepherd Home for Boys. They catch Jack's attention from outside the window as ideal candidates to provide Luke with a stable, loving environment.