Millie is a social worker and former housemaid who spent a decade in prison during her youth. She moves her family from a small apartment in the Bronx to a spacious house in Long Island, hoping to secure a better life for her children. Shortly after the move, she develops high blood pressure and becomes highly suspicious of her wealthy new neighbors and her husband's erratic schedule. She is highly protective of her children but struggles to accurately read the changing dynamics inside her own home.

Enzo is Millie's Sicilian husband who operates his own landscaping business. To afford their new Long Island home, he works long hours and frequently assists their neighbor Suzette with her yard in exchange for business referrals. Though he is a devoted father with a history of protecting women from danger, his recent late-night absences and secretive behavior cause friction in his marriage.

Suzette is a wealthy real estate agent who lives next door to the Accardi family. She presents a highly curated image of suburban perfection while routinely making condescending remarks about Millie's appearance and smaller house. She openly flirts with Enzo, frequently requesting his landscaping services and creating tension across the property line.

Jonathan is Suzette's pale, quiet husband who works in a lucrative finance position. He initially appears unpretentious and agreeable, contrasting sharply with his wife's status-obsessed personality. He spends considerable time inside his house and occasionally interacts with neighborhood children, including Nico, when they cross into his yard.

Nico is Millie and Enzo's energetic nine-year-old son. He loves playing baseball and initially makes friends easily at his new school. However, after breaking a window at the Lowells' house and doing chores to pay it off, his behavior changes drastically, resulting in sudden violent outbursts and emotional withdrawal.

Ada is Millie and Enzo's eleven-year-old daughter. She deeply misses her friends in the Bronx and struggles to adjust to her new school, where she faces persistent harassment from male classmates. She is highly observant, noting the behavioral shifts in her younger brother while keeping her own anxieties hidden from her parents.

Janice is an older, wealthy widow who lives across the street from the Accardis. She acts as the neighborhood watchdog, taking photographs of the neighboring houses and spreading warnings about Suzette and Enzo. She is highly protective of her son, Spencer, keeping him on a leash while waiting for the school bus.

Martha is a quiet housemaid who cleans for Suzette Lowell and eventually takes on hours at the Accardi house. She rarely speaks and maintains an intense, observant stare while working, which leads Millie to misinterpret her intentions.

Spencer is Janice's pale third-grade son who quickly befriends Nico at the bus stop. He lives under the strict, watchful supervision of his paranoid mother.

Benny is an NYPD officer and Ada's godfather. He is a trusted friend to the Accardi family who provides practical advice and assistance regarding law enforcement when they face trouble.

Cecelia is a skilled public defender whom Millie and Enzo cared for when she was a young girl. She provides legal counsel to the family when they face trouble in their new town.

Detective Willard is the lead police officer investigating a major incident in the Long Island neighborhood. He is thorough, highly suspicious of the Accardi family, and aware of Millie's criminal record.

Gabe is a boy at Ada's new school who persistently bothers her. He refuses to accept her clear rejections and physically grabs her wrist until Enzo intervenes.

Hunter is a student at Ada's school who continually harasses her during class and library time, ignoring her requests to stop and acting entitled to her attention.