An ex-policeman and frustrated writer who serves as a beta reader for Hannah Tigone's novel, expressing his thoughts and interpretations through his notes. There are two characters named Leo, with the narrative exploring their interactions with Freddie and the broader storyline.

A 30-year-old man with a complicated past and a connection to Freddie in the story-within-a-story. He is portrayed with a dual nature, reflecting both his charm and the darker, mysterious elements of his life.

An investigative journalist who conceals his true identity for much of the story-within-a-story. Known for his good looks and engaging demeanor, he has complex relationships with the other characters.

A former ballerina and psychology student with a distinctive style, including tattoos and piercings. She is portrayed as emotionally fragile, with her actions sometimes bordering on obsessive.

The author of the frame narrative, seen indirectly through the interactions and perceptions of Leo A. Her character influences the storyline through her writing decisions and interactions with the other characters.

A former surgeon whose struggle with prescription drug addiction affects his life and relationships. His character provides insight into themes of redemption and justice within the narrative.

Freddie Kincaid's curious downstairs neighbor who surprises others by claiming a medical background in a critical moment. Her actions reflect the narrative's exploration of reality versus imagination.

A sophisticated woman who is primarily defined by her role as Whit's mother, and she plays a part in the unfolding events involving Cain. Her character represents the complex social dynamics within the story.

A murder victim and ambitious investigative journalist with a connection to prominent figures in Boston society. Her absence from the central events highlights the mystery element of the narrative.