Louise is a native French woman over forty who works as a nanny for the Massé family. She lives alone in a rundown one-bedroom apartment in a Parisian suburb, facing hidden financial debt inherited from her late husband. At work, she is meticulous, cleaning the apartment, cooking meals, and organizing the household far beyond her required duties. This highly professional exterior masks severe isolation and mental health challenges.

Myriam is a criminal defense attorney and the mother of Adam and Mila. She speaks native Arabic and possesses the Hand of Fatima from her mother, which reflects her immigrant background. She feels stifled by domestic life and societal judgment, driving her decision to hire a nanny and resume her demanding legal career. She relies heavily on Louise to manage her household, choosing to overlook minor boundary crossings to maintain her professional freedom.

Paul is Myriam's husband and a music professional living in the 10th arrondissement of Paris. He holds rigid views about the people he employs, openly refusing to hire immigrants or women who wear veils. He happily accepts the conveniences Louise provides but views her strictly as hired help, often becoming irritated when her personal life or lower-class struggles intrude on his comfort.

Stéphanie is Louise's estranged, adult daughter who ran away from home as a teenager. During her childhood, she constantly struggled to fit into the upper-class environments of her mother's employers. She faced expulsion from a prestigious school, which embarrassed her mother and led to harsh physical discipline.

Mila is the older child of Paul and Myriam Massé. She is energetic and prone to throwing tantrums in public, knowing it embarrasses her caretakers. She develops a complex bond with her nanny, sharing an unspoken understanding after a violent physical altercation in the park.

Adam is the infant son of Paul and Myriam. Initially prone to crying at night, he is quickly soothed by Louise's massages and singing. He requires constant supervision, making his parents highly dependent on their nanny's consistent presence.

Wafa is an undocumented immigrant who works as a nanny in Paris. She becomes Louise's sole friend, inviting her to her home for dinner and including her as a witness at her wedding. She possesses a much more relaxed approach to her job compared to Louise's rigid and haughty professionalism.

Jacques is Louise's deceased ex-husband. He was emotionally and physically abusive, often criticizing her caregiving work with racist remarks. He accrued significant financial debt through failed lawsuits and lines of credit, which he left to Louise upon his death.

Captain Nina Dorval is the police detective assigned to the case involving the Massé family. She interviews neighbors, acquaintances, and landlords as she attempts to construct a timeline and understand the obscure motivations behind the events that transpired.

Rose Grinberg is a neighbor of the Massé family. She observes Louise's unusual and motionless behavior in the apartment building and later provides testimony regarding Louise's financial struggles and requests for extra work to make rent.

Emma is Myriam's friend and a fellow mother. She frequently posts beautiful, curated photos of herself and her children on social media. She represents a traditional embrace of motherhood that contrasts directly with Myriam's professional ambitions.

Sylvie is Paul's mother. She holds traditional, frugal views and previously criticized Myriam for devoting too much time to her legal career, which causes lingering friction whenever the family visits.

Dominique is Paul's father. He lives in the mountains and shares his wife's frugal, traditional lifestyle, expecting his son to adhere to their modest values during family visits.

Mr. Franck is one of Louise's former employers. When he learned that Louise was pregnant with Stéphanie, he arranged and offered to pay for an abortion, openly stating that a single woman in her financial position should not have children.

Genevieve Franck is an elderly woman who required full-time caretaking. Louise worked for her son and attended to Genevieve's needs before missing a scheduled medical appointment and abruptly abandoning the position.

Mrs. Rouvier is Louise's former employer. She highly recommends Louise's domestic services but previously enforced strict class boundaries when Louise's daughter visited their country house, ensuring the girl was treated as hired help rather than a guest.

Hector is the last child Louise cared for before joining the Massé household. As a young adult, he remembers sensing an unspoken menace in Louise's demeanor, despite her never being overtly harsh to him during his childhood.

Hervé is an older man who works part-time as a delivery driver. He meets Louise through Wafa, talks to her about books and music, and walks her to the metro station, inadvertently sparking her desire to secure long-term employment.

Lydie is a nanny who watches children at the same park Louise frequents. She notices the Massé children growing older and attempts to connect Louise with a pregnant woman seeking a nanny, but her offer is met with hostility.

Youssef is Wafa's partner. He marries her in a formal ceremony attended by Louise, which leads to a lively, celebratory restaurant dinner with their community.