Billie is a 35-year-old luxury travel consultant living in New York City. Having endured childhood trauma and her mother's early-onset Alzheimer's, she developed a fierce, dependent bond with her childhood best friend, Cassie. Despite building a rewarding career and avoiding the materialistic trappings of high society, Billie remains emotionally anchored to the past and struggles to accept that Cassie has distanced herself.

Cassie is a social media influencer and boutique owner who lives in a Manhattan penthouse. After her father lost his inherited wealth, she spent her youth in Red Hook, developing a fierce ambition to reclaim her place in high society. She carefully curates an idealized online persona to mask her anxieties, prioritizing status and wealth above authentic connections.

Wade is Lorraine's boyfriend and eventual husband. He is a highly predatory and manipulative man who capitalizes on Lorraine's failing memory to exert control over the household. His abusive presence deeply traumatizes Billie and acts as a catalyst for her unbreakable childhood bond with Cassie.

Lorraine is Billie's mother, who works as a dental nurse in Red Hook. Initially a loving and present single parent, she suffers from early-onset Alzheimer's disease. Her tragic cognitive decline leaves her unable to recognize her new husband's predatory nature or protect her daughter from his abuse.

Grant is a hedge fund manager who comes from old money. He provides Cassie with the luxurious Manhattan lifestyle she desires, completely removing her from her humble roots. However, he holds a patronizing attitude toward her online business, and his reliance on his trust fund frequently causes marital tension.

Alex is a New York City police officer who begins dating Billie. Down-to-earth and straightforward, he represents a sharp contrast to the wealthy, superficial elite of Cassie's circle. He is genuinely affectionate toward Billie but struggles to understand her enduring loyalty to a friend who repeatedly dismisses her.

Jane is the founder of the boutique luxury travel company, The Path, and Billie's boss. She lives an authentic life with her wife, Sasha, recently moving to the same Gramercy apartment building as Cassie. Jane acts as a practical voice of reason, pointing out the unbalanced and unhealthy nature of Billie's attachment to her past.

McKay is Grant's cousin and the quintessential "It Girl" from Cassie's Harvard days. Coming from an impeccable family pedigree, she represents the elite social status Cassie actively pursues. She successfully replaces Billie as Cassie's closest confidante, serving as Ella's godmother and acting as a gatekeeper to high society.

Remy is an artist who becomes Billie's first serious boyfriend during her time at Northeastern University. Gentle and understanding, his respectful demeanor contrasts sharply with the toxic masculinity of Billie's stepfather. He helps Billie process her trauma, though their relationship faces challenges over their differing views on having children.

Grandma Catherine is Cassie's paternal grandmother, a wealthy woman residing in an elegant Greenwich home. She cut off her son financially after he mismanaged his trust fund, but she maintains a relationship with Cassie. She serves as Cassie's aspirational role model, deeply instilling elitist values in her granddaughter.

Ella is Cassie and Grant's infant daughter. She is the center of Cassie's new identity as a mother and heavily featured on her Instagram account. Her sudden disappearance from the apartment terrace serves as the central crisis of the narrative.

Lourdes is the Hispanic housekeeper and nanny employed by Cassie and Grant. Despite being essential to the functioning of their household and the care of baby Ella, she is deliberately hidden from Cassie's online audience to maintain the illusion of an effortless lifestyle.

Sasha is Jane's wife. The couple maintains a healthy, authentic relationship and recently secured a dream apartment in Gramercy, placing them in the exact same building as Cassie.

Mara is Cassie's sister and a single mother who continues to live in their hometown of Red Hook. She is frequently sarcastic about Cassie's lavish lifestyle and actively points out Grant's condescending behavior during family visits.

Eric is Cassie and Mara's father. After losing his family inheritance through poor investments, he was cut off by his wealthy mother, Grandma Catherine. He moved his family to the more modest town of Red Hook, where he remains content despite Cassie's deep resentment of their lost status.

Detective Barringer is the police officer assigned to oversee the kidnapping case. He relies on practical evidence, theorizing that a group of teenagers might be involved, which frequently frustrates the paranoid and high-strung Cassie.

Kyle is Cassie's first high school boyfriend from Red Hook. He becomes an early casualty of Cassie's developing social ambitions after Grandma Catherine ruthlessly criticizes his working-class appearance during a lunch trip to Greenwich.

Ashton is a childhood friend from Red Hook who frequently mocks Billie's weight. She later grows closer to Cassie during their senior year of high school, taking Billie's place temporarily after the two have a falling out.