Frank is a thirteen-year-old boy living in the working-class Flats of New Bremen, Minnesota. As the middle child of a Methodist minister, he observes the adult world with an intensely curious perspective. His tendency to eavesdrop through church air ducts and investigate local events constantly places him at the center of the town's unfolding tragedies. He relies heavily on his younger brother for moral grounding as he begins to question his family's faith.

Nathan is a devout Methodist minister who presides over three local churches in the New Bremen area. Originally planning to become a wealthy lawyer, his experiences making fatal battlefield decisions in World War II profoundly altered his life trajectory, leading him to the clergy. He demonstrates quiet virtue, consistently choosing to do what he believes is morally correct even when it draws the ire of his family or the wider community.

Ruth is Nathan's wife and the choir director for his church. Unlike her husband, she wrestles deeply with her faith and openly expresses dissatisfaction with her life as a minister's wife in a small town. She drinks, smokes, and harbors resentment over the loss of the affluent, urban future she imagined for herself. She actively pushes her daughter Ariel toward broader horizons to ensure Ariel avoids a similarly restricted life.

Ariel is the eighteen-year-old eldest child of the Drum family. She possesses immense musical talent as a singer, organist, and pianist, and holds an acceptance letter to Juilliard for the upcoming fall semester. Born with a cleft lip that was surgically repaired, she operates as the golden child of the family. Despite her perfect exterior, she maintains an independent social life that she hides from her parents.

Jake is the ten-year-old youngest child of the Drum family. He has a severe stutter that subjects him to mockery from town toughs and police officers alike. Despite his youth, he serves as the moral compass for his older brother Frank. He possesses a highly sensitive nature and approaches the world with an optimistic, devout perspective that contrasts sharply with his family's growing cynicism.

Emil is a blind, disfigured World War II veteran and former Hollywood music composer. He lives in a renovated farmhouse on the outskirts of New Bremen overlooking the river. Before the war, he broke an engagement with Ruth Drum to pursue fame in New York. He dictates his memoirs to Ariel Drum, forming a close bond over their shared musical talents while battling intense, morbid depression.

Lise is Emil's younger sister. Born deaf, she lives a highly isolated life with her brother on the edge of town, largely abandoned by the wealthy Brandt relatives. She avoids the community entirely, spending nearly all her time tending to her extensive flower gardens. She despises physical contact, reacting with violent panic if touched by anyone other than Emil or Jake Drum.

Karl is the wealthy, attractive son of the local brewery owner. He dates Ariel Drum and treats her younger brothers with easy kindness. He plans to attend St. Olaf College to play football before eventually returning to run his family's business. His affluent upbringing in the Heights places him in sharp contrast to the working-class residents of the Flats.

Gus is Nathan Drum's close friend and former military subordinate from World War II. He lives rent-free in the basement of the Methodist church in exchange for maintaining the building's furnace. He drinks heavily and gambles, often running afoul of the law, but provides steady, non-judgmental guidance to Frank and Jake when they face ethical dilemmas.

Ruth's father is a local resident who married his former secretary, Liz, after his first wife passed away. He views Nathan Drum as a financial and professional failure for abandoning a law career for the clergy. He occasionally employs Frank and Jake to do yard work, though his presence frequently brings tension into the Drum household due to his vocal disapproval of Nathan.

Axel and Julia are Karl Brandt's parents. Axel inherited and runs the town's highly successful brewery, establishing the family firmly in the wealthy Heights neighborhood. Julia grew up in the working-class Flats before marrying Axel, leading to an ongoing, icy feud with Ruth Drum over class, status, and their respective children's futures.

Warren is a Dakota Sioux World War I veteran who lives a marginalized existence near the Minnesota River. He maintains a driftwood lean-to on the riverbank where he fishes and keeps a buried tin can of scavenged belongings. He holds a deep, historical grievance regarding the treatment of his people by white settlers and operates entirely outside the town's social and religious structures.

Bobby is a developmentally disabled adolescent boy living in New Bremen. He enjoys spending time near the railroad tracks watching the trains pass. His sudden death on the train trestle initiates the dark events that unfold over the summer of 1961.

"The Skipper" is an unidentified itinerant man found dead near the railroad tracks early in the summer. Redstone deduces his nickname and veteran status from items in his pockets, including a faded photograph of a wife and child that hints at a tragic past.

Morris is the resident town tough of New Bremen. He wears black leather jackets, slicks his hair into a ducktail, and drives a customized 1932 Ford Deuce Coupe with flames painted on the sides. He frequently clashes with Frank and Jake, acting as a looming physical threat to the younger boys.

Officer Doyle is a local police officer who regularly patrols New Bremen. He exhibits a cruel, sadistic streak, demonstrated by his casual violence toward animals and his aggressive questioning of children. He views outsiders with extreme prejudice and frequently abuses his authority under the guise of maintaining order.

Danny is Frank's childhood friend and neighbor. He is half-Dakota Sioux and provides Frank's main connection to Warren Redstone. He frequently joins Frank and Jake in their summer explorations around town and the river valley.