Nora's father, a phlebotomist, and convicted serial killer, serving multiple life sentences. Known for his charm and danger, his relationship with Nora is central to the novel's tension.

Nora's sister and assistant at her medical practice, whose background and motivations unfold throughout the story. Harper is portrayed as charming yet complex, with a hidden connection to Nora.

Nora's former college boyfriend who reconnects with her as an adult. Known for his kindness and charm, he represents a potential for renewed happiness in Nora's life.

Nora's medical partner, known for his flashy style and outgoing personality, contrasting with Nora's frugality. He is depicted as a popular, charismatic doctor.

The deceased wife of Aaron Nierling and mother of Nora and Harper. Her past and potential involvement with Aaron's crimes remain ambiguous.

The detective investigating Nora for the murder of two patients, known for his persistence and professional demeanor. His role is primarily functional, driving the investigation forward.