Clay is the fourth of five Dunbar brothers, living in a chaotic, parentless household on Archer Street. He is exceptionally athletic, focusing his energy on grueling runs and absorbing physical punishment in organized fights at a local athletic track. Though quiet and often teased by his siblings for his silence, he absorbs his family’s stories and holds onto a deep, unspoken grief. When his estranged father returns to ask for labor, Clay alone entertains the request.

Matthew is the eldest Dunbar boy and the pragmatic head of the household, serving as the narrator of the story. After his mother’s death and father’s sudden departure, he dropped out of school to work in construction and pay the bills. He shoulders the burden of raising four wild brothers with a mixture of stern discipline and fierce loyalty. His deep-seated anger toward his father shapes the household's hostile stance against the man's return.

The second eldest Dunbar brother is defined by his combative nature and quick temper. Rory channels his anger regarding his family’s fractured state into physical altercations, frequently acting out in destructive ways. He pushes Clay into increasingly brutal physical tests at the Bernborough track, acting as the primary physical instigator among the brothers.

Henry is the third Dunbar brother, utilizing his natural charisma and intelligence as a distraction from his grief. He operates various money-making schemes, arranging sports bets and flipping items discovered at local garage sales. Highly talkative and business-minded, he provides a sharp contrast to Clay’s silence and Rory’s physical aggression.

The youngest Dunbar brother possesses a sensitive disposition and heavily relies on his older siblings for stability. He channels his energy into collecting and caring for a growing menagerie of household pets, each named after figures from classical mythology. His presence encourages his older, rougher brothers to show flashes of gentleness amidst their chaotic daily routines.

Michael is the patriarch of the Dunbar family, heavily resented by his older sons who refuse to call him "father" and refer to him strictly as "the Murderer." Originally an aspiring artist from the town of Featherton, he abandoned his five sons six months after the death of his wife. He returns to the city seeking assistance to construct a bridge on his rural property in Silver, initiating a profound rift among the brothers.

Penelope is the late mother of the Dunbar boys, originally born in the Eastern Bloc as Penelope Lesciuszko. A skilled pianist and lover of Greek mythology, she escaped a communist regime as a teenager and immigrated to Australia as a refugee. She worked as a cleaner and later as a teacher. Her battle with cancer and subsequent passing serves as the central tragedy that shatters the Dunbar household.

Carey is a determined teenager who moves into the house next door to the Dunbars. Coming from a family of jockeys, she stubbornly pursues an apprenticeship in professional horse racing despite her parents' initial resistance. She forms a quiet, closely regulated bond with Clay, meeting him secretly on Saturday nights in an overgrown lot called The Surrounds.

Claudia is a teacher at the local school who takes a sympathetic interest in the Dunbar family's situation. She provides Clay with reading materials and extends a warm, steady presence to Matthew as he shoulders his heavy adult responsibilities.

Abbey is Michael Dunbar's teenage girlfriend from his hometown. She plays a significant role in his early adult life, encouraging his artistic development and sitting as the subject for his earliest portraits before their relationship eventually fractures under the pressure of their differing ambitions.

Ennis is a highly respected and renowned horse racing trainer. He maintains strict expectations for his riders, insisting they eliminate unnecessary distractions and relationships from their lives to focus entirely on the grueling physical demands of the sport.

Achilles is a mule purchased by the Dunbar brothers using Clay's athletics winnings. He serves as a chaotic but beloved addition to the family's collection of animals, frequently breaking into the house and standing as a physical symbol of the boys' unorthodox, parentless lifestyle.