27-year-old Wilhelmina “Millie” Calloway is a young woman living in her car and desperate for steady work after serving ten years in prison. She accepts a lucrative live-in housekeeper position for the Winchester family. Despite her criminal record and the unsettling lock on the outside of her tiny attic room, she works hard to maintain her employment and adhere to her parole terms. She tries to keep a low profile in her new role, hoping to save enough money to secure her independence.

Nina is a wealthy woman in her late thirties who employs Millie as her live-in housekeeper. She oscillates between being warm to Millie and behaving erratically, often destroying rooms and blaming Millie for the mess. Local neighborhood gossip suggests she has a history of psychiatric hospitalizations following an incident with her daughter. She constantly wears white clothing and demands an impossibly clean household.

Andrew is a wealthy CEO and Nina's husband. He frequently attempts to pacify his wife's explosive moods and apologizes to Millie for the resulting chaos. He presents himself as a devoted, long-suffering spouse who desperately wants another child. He frequently extends kindness to Millie, creating a sharp contrast to his wife's hostility.

Cecelia is Nina's nine-year-old daughter. She is blonde, blue-eyed, and frequently dressed in white, frilly clothing. She exhibits rigid demands regarding her meals and daily routine, often throwing tantrums if her food does not meet exact brand and shape specifications.

Enzo is the handsome, Sicilian landscaper who maintains the Winchester family's garden. He communicates almost exclusively in Italian, leading most of the neighborhood to assume he speaks no English. He observes the household dynamics closely from the yard and repeatedly attempts to warn Millie about the danger of working there.

Evelyn is Andrew's mother. She holds strict beliefs about discipline, neatness, and child-rearing. She frequently criticizes Nina's parenting style and household management, influencing her son's expectations for a perfect home.

Pam is Millie's parole officer. She monitors Millie's employment status and housing situation. She encourages Millie to reintegrate into society by making friends and building a stable, lawful life.

Suzanne is a local mother in the Winchester family's wealthy social circle. She participates in the neighborhood gossip regarding Nina's mental health and home life, maintaining a superficial friendship with her.

Amanda is a nanny working for another family in the neighborhood. She provides Millie with painkillers for a headache and readily shares disturbing local rumors about Nina's past hospitalizations.

Patricia is a local mother in the PTA who interacts with the Winchester household. She casually drops information about Nina's activities and tracking habits while shopping.