Eileen is a twenty-four-year-old secretary living an unhappy life in the bleak New England town of X-ville. She works at a juvenile penitentiary and spends her free time acting as a reluctant caretaker for her paranoid father. She struggles with profound depression and social isolation, along with severe body dysmorphia. She copes by wearing her deceased mother's oversized clothing and quietly fantasizing about escaping to New York City.

Rebecca is a recent Harvard graduate who arrives in X-ville to oversee a new education program for the juvenile inmates. She is a tall, conventionally beautiful woman who possesses a confident demeanor that immediately captivates Eileen. She rejects traditional societal expectations for women and easily charms those around her with calculated flattery.

A former police officer who lives in a state of alcohol-induced paranoia. He relies entirely on Eileen for his daily needs, including his constant supply of gin. He is verbally abusive and believes mysterious enemies are conspiring against his household, occasionally acting out aggressively toward the local community with his firearm.

Joanie is Eileen's older sister who left the family home at age seventeen. She lives with her boyfriend in X-ville and enjoys a life of relative freedom, unburdened by the responsibility of caring for their ailing father. Her independence and comfort in her own body make her a subject of intense envy for her younger sister.

Eileen's recently deceased mother suffered from a painful illness that required Eileen to drop out of college to act as her nurse. When alive she was aggressively nonreligious. She frequently criticized her daughter's appearance and struggled with her own alcohol addiction, leaving a lasting negative impact on Eileen's self-image.

Randy is a former Moorehead inmate who now works as a guard at the facility. He is completely unaware that Eileen spends her weekends secretly watching his apartment and entertaining obsessive daydreams about him.

Leonard is a teenage boy incarcerated at the juvenile facility for the crime of patricide. He has remained entirely mute since his imprisonment and quickly becomes a subject of interest for the facility's new educational director.

Mrs. Polk is Leonard's mother, a quiet woman who attempts to visit her son at the juvenile penitentiary. To Eileen, she represents the restrictive traditional domestic life of married women in X-ville.

Mona was the family's dog who died shortly before Eileen's mother passed away. She is one of the only beings Eileen ever felt true affection for, and Eileen secretly buried the dog in the yard by herself.

Dr. Frye is the retiring psychiatrist at Moorehead. He is part of the established institutional system that governs the facility before the arrival of new, younger staff members.

Dr. Morris is the new psychiatrist hired to replace Dr. Frye at Moorehead. He arrives at the facility on the same day as Rebecca.

Aunt Ruth is Eileen's aunt who visits the house weekly to take Eileen's father to Sunday Mass. Her visits require Eileen to temporarily unlock the car trunk to return her father's confiscated shoes.