Marcus is a 28-year-old, highly successful but blocked author living in New York. Desperate to meet his publisher's deadline, he seeks refuge and inspiration with his former college professor in Somerset, New Hampshire. When his mentor is accused of a decades-old crime, Marcus assumes the role of amateur investigator, driven by a complex mix of loyalty, ambition, and a desire to overcome his creative stagnation.

Harry is a 67-year-old, highly respected literary figure whose tranquil life in Somerset shatters when police unearth a body in his yard. Back in 1975, he was a struggling 34-year-old writer who arrived in the small coastal town looking for inspiration. He harbors deep secrets about his summer in Somerset and his connection to the young girl who vanished.

Nola is the 15-year-old daughter of the local reverend in Somerset. Beautiful, mature for her age, and deeply sensitive, she works weekend shifts at the local diner and draws the attention of several town residents. Her disappearance in the summer of 1975 leaves a lasting scar on the community and forms the central mystery of Marcus's investigation.

Luther is an artistic, gentle man working as a driver for a wealthy local businessman. A brutal gang attack in his past left him severely disfigured and largely isolated from society. He channels his emotions and observations of the world into painting.

Travis is the current chief of police in Somerset. In 1975, he was a young, timid patrol officer desperately trying to muster the courage to ask out his crush at the local diner. He assists Marcus early in his investigation by providing details about the initial search for Nola.

Jenny is the owner of Clark's, a popular diner in Somerset. In 1975, she was a 24-year-old waitress, former cheerleader, and the town's undisputed golden girl. She develops a powerful, obsessive attraction to Harry Quebert upon his arrival in town, viewing him as a ticket to a more glamorous life.

Tamara is the harsh, domineering matriarch of the Quinn family. She runs the local diner with an iron fist and constantly bullies her husband. Highly ambitious, she schemes to set her daughter up with the visiting writer, showing little empathy for the people she uses to climb the social ladder.

Robert is Tamara's quiet, seemingly passive husband. He works alongside his family at Clark's diner, often serving as the target for his wife's relentless complaining. Beneath his meek exterior, he pays close attention to the town's dynamics and harbors deep affection for his family.

David is Nola's father and the former reverend of Somerset. Originally from Alabama, he moved his family north to start over. In the present day, he is a frail, grief-stricken man who continually blasts loud music to punish himself for his perceived failures in protecting his daughter.

Roy is the aggressive, commercially driven head of the Schmid & Hanson publishing house. He views literature entirely as a product, pushing Marcus to exploit the tragedy in Somerset for maximum profit. He cares little for ethics or accuracy, prioritizing sensationalism and sales above all else.

Perry is a gruff, no-nonsense police sergeant tasked with investigating the modern-day discovery of the remains. Though initially hostile toward the amateur sleuth, he gradually forms an unofficial, bickering partnership with Marcus as they re-examine the old clues together.

Gareth Pratt was the chief of police in Somerset during the summer of 1975. He led the initial search for the missing girl, though Marcus's modern-day inquiries raise questions about the thoroughness and integrity of his original investigation.

Elijah is a powerful, affluent businessman from the nearby city of Concord. He employs a distinctive chauffeur and holds considerable influence over the region, intertwining himself with the lives of several Somerset residents through financial arrangements and patronage.

Douglas is Marcus's literary agent. He attempts to manage his client's severe creative block while facing the intense pressure from the publishing house, frequently advising Marcus on how to frame his investigation for maximum public interest.

Louisa is David's wife and Nola's mother. Her presence in the Kellergan household casts a long, dark shadow over Nola's upbringing, contributing to the family's troubled dynamic and Nola's desire to escape Somerset.

Nancy is a local Somerset girl and one of Nola's school friends. She provides Marcus with crucial context about Nola's behavior during the summer of 1975, including the teenager's secretive relationships and home life.

Deborah is a Somerset resident who frequently calls the local police station. On the day of the disappearance, she becomes a crucial witness after spotting a girl in a red dress running through the forest near her home.

Benjamin is the attorney hired to defend Harry Quebert against the murder charges in 2008. He works closely with Marcus to gather information, hoping the writer's amateur investigation will uncover evidence to exonerate their client.

Sylla is Luther Caleb's sister. She provides the investigators with insight into her brother's life before his disfiguring accident, painting a picture of a handsome, promising young man whose life was derailed by violence.

Ernie is the local librarian in Somerset. He serves as a barometer for the town's shifting opinions, initially welcoming Marcus but later expressing the community's outrage when the investigation unearths uncomfortable local secrets.