Armand is the former Chief Inspector of Homicide who assumes a new role as the head of the Sûreté Academy. He is a highly moral and responsible man who seeks to root out long-standing corruption in the police force. With a calm and commanding presence, he mentors vulnerable cadets and attempts to extend grace to those who have made serious mistakes in their past.

Amelia is a twenty-year-old cadet at the academy with a history of drug use and sex work. She stands out from her peers with her multiple tattoos and piercings, acting tough to mask her deep insecurities about belonging in a prestigious program. Despite her rough exterior, she possesses sharp intelligence, a fascination with poetry, and a desperate desire to turn her life around.

Serge Leduc is a corrupt, sadistic professor and second-in-command at the Sûreté Academy. He uses his power to torment vulnerable cadets, teaching them that citizens are the enemy and demanding absolute loyalty. He views the academy as his personal domain and deeply resents Gamache's arrival, actively working to undermine the new ethical reforms.

Michel is the disgraced former Chief Superintendent of the police force who resigned after his involvement in a major corruption scandal was exposed. He lives in rural isolation until Gamache surprisingly offers him a teaching position at the academy. He carries the heavy weight of his past betrayals while trying to manage his return to the law enforcement world.

Reine-Marie is Armand Gamache's wife, a trained archivist living in the quiet village of Three Pines. She applies her professional skills to help the local villagers sort through historical papers found hidden in the walls of the bistro. She provides steady, grounding support to her husband as he takes on the immense stress of reforming the academy.

Jean-Guy is a seasoned homicide detective and Gamache's former second-in-command in the homicide department. He accepts a position to continue working under Gamache at the academy. He is fiercely loyal to his father-in-law and prepares for his first child with his wife, Annie.

Isabelle is the head homicide investigator for the Sûreté du Quebec. She is a highly intelligent, elegant professional whose previous television interview inspired Amelia Choquet to pursue police work. She steps in to lead the investigation at the academy with clear-eyed objectivity.

Paul is a high-ranking Deputy Commissioner in the Royal Canadian Mounted Police. He is brought in from outside the Sûreté to oversee police investigations at the academy to ensure total transparency. He is highly observant and quickly becomes suspicious of Gamache's protective actions and hidden motives.

Huifen is a third-year cadet at the Sûreté Academy. She is selected by Gamache to join a small group of students tasked with a specialized assignment regarding a whimsical map of Three Pines.

Nathaniel is a first-year cadet at the Sûreté Academy who participates in Gamache's specialized mapping exercise. He maintains the academy tradition of serving breakfast to professors and stays with the poet Ruth while in Three Pines.

Jacques is a third-year cadet at the Sûreté Academy. He openly admires Professor Leduc, believing the man's harsh methods make the cadets tougher, and frequently displays open disrespect toward Gamache and the civilians in Three Pines.

Olivier is the co-owner of the local bistro in Three Pines alongside his partner Gabriel. He frames the strange orienteering map found in the bistro's walls as a thoughtful gift for Gamache and helps manage the logistics of housing the cadets.

Gabriel, often called Gabri, is Olivier's partner and the co-owner of the Three Pines bistro. He enthusiastically assists the villagers in their historical research project regarding the old papers found hidden in his establishment.

Ruth is a famous, cantankerous poet who lives in Three Pines. Despite her abrasive exterior and sharp tongue, she works closely with the other villagers on their archival project and provides housing for the cadet Nathaniel.

Clara is a painter living in Three Pines who frequently hosts village gatherings and dinners. She steps up to board Amelia Choquet when Gamache brings the cadets to the village for their protection.

Myrna is a retired psychologist who runs the local bookstore in Three Pines. She is a highly supportive member of the community who boards Jacques Laurin, maintaining her composure despite his obvious disrespect toward her.

Annie is Armand and Reine-Marie Gamache's daughter, who is currently pregnant with her first child. She deeply trusts her father's integrity and supports her husband's stressful transition to his new role at the academy.

Therese is the current police superintendent who reviews and approves Gamache's sweeping reform plans for the academy. She expresses significant shock at Gamache's controversial decision to hire the disgraced Brébeuf.

Professor Godbut is an instructor at the academy known for his cruelty and abusive behavior toward the students. Investigators suspect him of being involved in the corrupt contracting practices that plague the institution.

Charpentier is a professor of tactics at the Sûreté Academy who harbors a deep, almost poetic fascination with maps. He becomes highly intrigued by the Three Pines orienteering map and accompanies Gamache to study the village's stained-glass window.

Mayor Florent is the civic leader of St. Alphonse, a town with a bitter relationship with the academy. He openly expresses his intense hatred for Leduc and the institution's presence on disputed community land.

Elizabeth is an employee at the McDermot Revolver Company in Europe. She fields international phone inquiries regarding the rare antique-style revolver found at the academy, providing hesitant but crucial assistance to the police.

Antony Turcotte is a highly significant historical figure in Quebecois cartography known for mapping the Eastern Townships region. He is the credited creator of the detailed, whimsical orienteering map found in the walls of the Three Pines bistro.

Marie Valois is a woman from the early twentieth century who lived in the building that eventually became the Three Pines bistro. Historical records show she experienced devastating tragedy when her sons went to fight in World War I.

Frederick Valois is the late husband of Marie Valois who died young. Historical records note that he worked as a mapmaker.

Gracie is a small, unappealing rescue puppy adopted by Reine-Marie. As the runt of her litter, she symbolizes the Gamache family's tendency to protect and nurture the most vulnerable beings in their orbit.