Joanne is a first-time mother in her thirties dealing with post-partum exhaustion and isolation in a remote, overly large countryside house. Having paused her real estate career to raise her infant, she craves adult interaction and initially welcomes the arrival of her stepdaughter. Her confidence wavers severely under household tensions and her husband's dismissive attitude toward her concerns.

Chloe is Richard's twenty-year-old daughter who recently dropped out of a fashion photography program in London. She carries trauma from her mother's tragic death and displays drastically different personalities depending on who is in the room. Around her father, she acts sweet and girlish, but she behaves coldly and critically when left alone with Joanne.

Richard is a business owner in his early fifties who provides a wealthy lifestyle for his family but frequently leaves them alone in a remote house. He feels guilty for sending his eldest daughter away to boarding school during her youth. He remains fiercely defensive of Chloe and dismisses his wife's anxieties as manifestations of post-partum mental illness.

Evie is Joanne and Richard's four-month-old daughter. She struggles to sleep and requires constant care, anchoring Joanne to the house. She functions as the center of an escalating power struggle between her mother and her new half-sister.

Diane was Richard's first wife and Chloe's mother. She died falling from a third-floor balcony when Chloe was eleven years old. Her death was officially ruled a suicide and continues to cast a dark shadow over the Atkinson family.

Roxanne is the housekeeper for the Atkinson family. She prefers to keep a professional distance, frequently wearing earbuds to avoid Joanne's attempts at casual conversation. She occasionally spends time with Chloe instead.

Robyn is Joanne's childhood best friend. She works at a law firm and serves as a vital external sounding board, validating Joanne's anxieties when the rest of the household dismisses them.

Simon is the gardener at the Atkinson estate. He performs general maintenance tasks, including installing new locks, and unknowingly becomes part of Chloe's manipulative schemes when she insists on taking selfies with him.

Shelly is a former real estate colleague of Joanne. She offers Joanne the opportunity to take on some remote work, providing a temporary mental escape from full-time motherhood.

Jim is a local journalist who reported on the suspicious circumstances surrounding Diane's death. He remembers the case clearly and provides Joanne with unsettling historical details regarding the Atkinson family.

Solomon is the Atkinson family solicitor. He handles Richard's legal affairs, estate planning, and issues related to family wills.

Helen is Diane's mother and Chloe's maternal grandmother. She maintains a strained, fearful distance from her granddaughter, harboring long-standing suspicions about the tragedies that befell her family.

Sophie was Richard and Diane's infant daughter who died of a sudden cot death at three months old. Richard avoids mentioning her to Joanne because the memory remains painful.

Alfred is Richard's business partner who allegedly covered for Richard's whereabouts during a business trip years ago.

Isabella is Richard's ex-fiancée. Her infidelity ended their relationship, allowing Richard and Joanne, who was acting as their real estate agent, to eventually start dating.

Anthony is an old real estate colleague of Joanne. Richard harbors strong jealousy toward him, prompting Joanne to assure her husband she will not work directly with Anthony.

Oscar is Joanne's loyal pet labrador. He provides her with basic companionship in the empty countryside estate and accompanies the family on trips into town.