Twenty-five-year-old Jules is struggling financially after losing her administrative job and catching her boyfriend cheating. Orphaned and carrying the trauma of her older sister's unsolved disappearance, she hopes a lucrative apartment-sitting gig at the illustrious Bartholomew building will provide financial stability. She possesses a deep emotional attachment to the building due to a childhood favorite novel set there.

Ingrid is a young woman apartment-sitting in unit 11A, located just below Jules. Dealing with her own financial struggles and lacking a strong support system, she openly admits to feeling the psychological weight of the Bartholomew's strict rules. She forms a quick connection with Jules over their shared circumstances and need for income.

A young surgeon residing in apartment 12B. He comes from a long line of doctors and inherited his unit from his parents. He presents himself as a caring, welcoming neighbor who is willing to bend the building's strict rules to help Jules adjust to her new environment.

A prominent resident of the Bartholomew and the author of Heart of a Dreamer, a novel Jules has cherished since childhood. Having written her famous book while living in her parents' old apartment following a divorce, she maintains an elite status within the building's social hierarchy.

The manager of the Bartholomew. She strictly enforces the building's rigid code of conduct, ensuring that temporary apartment sitters do not bother the permanent residents or speak about the property publicly. She screens applicants rigorously to maintain the building's exclusive reputation.

Jules's loyal best friend. She provides a couch for Jules after a bad breakup but remains deeply skeptical of the Bartholomew. She actively researches the building's dark history and begs Jules to reconsider the job, offering her own money to keep Jules away from the property.

Another apartment sitter residing at the Bartholomew. Like Jules and Ingrid, he lacks a strong family network and needs the generous weekly pay. He harbors deep suspicions about the building's history regarding temporary tenants.

The door attendant at the Bartholomew. He manages the lobby traffic, assists residents with lost items, and acts as the frontline staff for the building's daily operations.

An actor and permanent resident of the Bartholomew. She represents the elite, upper-class demographic of the building's permanent tenants and dotes entirely on her dog.

Jules's ex-boyfriend. His infidelity serves as the catalyst for Jules losing her housing and eventually seeking the position at the Bartholomew out of sheer desperation.

Jules's older sister who went missing years prior. She used to read Greta Manville's novel to Jules, and her unresolved disappearance continues to shape Jules's fears and motivations.

An elderly, permanent tenant at the Bartholomew who suffers from heart trouble and requires assistance from a full-time caretaker.

Mr. Leonard's caretaker. She utilizes the building's basement and service areas to assist her employer, occasionally crossing paths with the temporary sitters.

A physician attending to Jules in the unfamiliar medical facility where she regains consciousness following an accident outside the Bartholomew.

A man present in the hospital room when Jules wakes up, acting as an attendant who monitors her recovery and listens to her story.

The young woman who occupied 12A before Jules. She vacated her position under unclear circumstances, prompting management to hire Jules to fill the vacancy.