Alix is a 45-year-old podcaster and journalist living in an affluent London neighborhood. Having recently concluded her successful interview series, she searches for a new subject. She maintains a curated public image that hides the private stress of her husband's severe alcohol addiction. She agrees to interview a local woman who shares her exact birthdate, inadvertently opening her home and life to intense scrutiny.

Josie is a 45-year-old woman who works part-time altering clothes at a shop called Stitch. She lives a quiet, isolated existence in a small flat overlooking a busy bus stop, initially wearing a wardrobe composed almost entirely of denim. Dissatisfied with her life and eager for change, she deliberately approaches a local podcaster to document her personal transformation. Her motivations quickly appear obsessive as she begins stealing small items and attempting to mirror the podcaster's lifestyle.

Walter is Josie's retired husband. He met Josie when she was a young teenager while he was working as a contractor on her mother's estate. He spends his days in their flat watching television or using his laptop. He maintains a quiet but tense dynamic with his wife, occasionally warning outsiders not to trust her version of events.

Nathan is Alix's husband, a successful professional working in office real estate. While he is generous and supportive of his wife's career, he struggles with a severe alcohol addiction. He frequently disappears on overnight drinking binges to cope with past family tragedies, creating significant instability in his marriage.

Erin and Roxy are the adult daughters of Josie and Walter Fair. Roxy is the eldest by two years and left the family home when she was sixteen following a turbulent childhood marked by behavioral challenges. Erin, the youngest, lives a reclusive existence in her bedroom, eating baby food and spending her time as a passionate online gamer.

Pat is Josie's mother, a confident woman who lives on a council estate. She presents herself as put-together and glamorous, demanding attention and respect from those around her. Her relationship with her daughter is openly hostile, marked by mutual dislike and a history complicated by her past connection to her son-in-law.

Brooke is Roxy's first girlfriend and a frequent presence at the Fair household during the girls' teenage years. Her sudden disappearance after a prom night remains a significant, unresolved mystery hovering over the neighborhood.

Katelyn is an aspiring actor who grew up in the same neighborhood as Josie. They cross paths at the local alterations shop, leading Josie to hire her for a specific, undisclosed task. She is instructed to approach Nathan at a bar and feign interest in him.

Zoe is one of Alix's sisters. She shares a close, supportive bond with Alix, characterized by a stylish, casual aesthetic. Alix frequently worries about Zoe discovering the extent of Nathan's drinking problems due to Zoe's protective nature.

Maxine is Alix's other sister. Alongside Zoe, she forms a tight-knit triad of siblings who support each other. Like Zoe, she represents the judgment Alix fears regarding her struggling marriage to Nathan.

Detective Constable Sabrina Albright is a police officer who becomes involved when the tensions between the Summer and Fair families escalate. Alix knows her from a previous professional interview, making her a trusted contact.

Helen is a childhood friend of Josie Fair. She provides outside perspective on Josie's teenage years, remembering her as a controlling and jealous companion before Walter entered the picture.

Mandy is the office manager at the school attended by both the Summer and Fair children. She remembers the Fair family's history of behavioral issues and provides Alix with early clues about their household dynamics.

Gio is a friend of Nathan Summer who frequently accompanies him on his late-night drinking binges, serving as an enabler for Nathan's struggles with alcohol.

Eliza is the young daughter of Alix and Nathan Summer. She lives in their affluent home and attends the local private school, representing the comfortable family life that Josie covets.

Leon is the young son of Alix and Nathan Summer. He is observant enough to notice when guests behave strangely in their home, alerting his mother to Josie's eavesdropping.

Jason is Walter's son from his first marriage. After Walter left his mother for the teenage Josie, Jason's mother moved the family to Canada. He has not seen his father since he was ten years old.