Chief Superintendent Sylvan Francoeur is a powerful and corrupt antagonist within the Sûreté, known for his authority and strategic manipulation. He is distinguished by his gray hair and confident bearing, with strong connections to influential figures in Québec.

Jean-Guy Beauvoir was once Gamache’s close colleague but is now dealing with trauma and addiction, which have complicated their relationship. Once energetic, he is depicted as struggling with personal demons and his loyalty in a department led by Francoeur.

Isabelle Lacoste, now third in command, remains a loyal and patient member of Gamache's team, frustrated by the incompetence within the Sûreté. Her intuition and steadfastness in following her instincts are key attributes.

Constance Ouellet, whose murder sets off the novel's events, is known for her privacy and struggles with opening up. She briefly appears as a kind individual whose actions show a desire for connection during her time in Three Pines.

Myrna Landers, a former psychologist, is a consistent presence in Three Pines known for her calm and reassuring nature. As the owner of the local bookstore, she protects her friend Constance's memory after her disappearance.

Clara Morrow is an artist living in Three Pines, part of Gamache’s circle there. Her role involves supporting her friend Myrna and representing the close-knit community through her creativity and emotional insight.

Ruth Zardo is an eccentric poet in Three Pines known for her sharpness and seemingly harsh demeanor. She is soft-hearted beneath her gruff exterior, showing affection in unique ways.

Thérèse Brunel, a Superintendent at the Sûreté, is a petite and determined ally to Gamache. Her integrity and experience provide her with a key role in aiding his investigation.

Jérôme Brunel, a retired doctor passionate about puzzles, assists Gamache through his amateur expertise in computers. He is noted for his brilliant mind and plays an integral role in uncovering vital information.

Yvette Nichol, working in the subbasement at the Sûreté, assists Gamache despite previous issues. Disheveled and often harsh, she shows willingness for growth and dedication.

Martin Tessier is Francoeur’s supportive subordinate, mainly interacting with Beauvoir. He contributes to maintaining the cycle of influence and pressure within the Sûreté.