Janice is a woman in her late forties living in Cambridge who works as a self-employed house cleaner. Plagued by vague feelings of guilt from her past, she prefers to fade into the background, quietly collecting the life stories of her clients rather than confronting her own unfulfilling marriage or childhood memories. She is empathetic, observant, and deeply devoted to the people and pets she cares for.

Mike is Janice's husband, a man who cycles through dozens of jobs over their decades-long marriage. Prone to giving unsolicited advice and criticizing his employers, he relies on Janice's steady income to keep them afloat. He views his wife as a reliable constant rather than a complex person, remaining entirely oblivious to her internal life.

Mrs. B is the gruff, formidable 92-year-old mother of Tiberius. She lives in an eccentric home built into the wall of one of Cambridge's oldest colleges. She possesses a sharp intellect and a secretive past involving espionage alongside her late husband. She challenges Janice by refusing to be just another cleaning client, instead spinning a serialized tale about a woman named Becky.

Euan is a Scottish substitute bus driver who travels to different routes to fill in for staff shortages. He is observant and kind, noticing Janice on his route and eventually initiating a conversation. Like Janice, he collects pieces of other people's lives—specifically their conversations. He carries unspoken past burdens with a gentle, pragmatic acceptance.

Tiberius is Mrs. B's son and the owner of the fox terrier Decius. Arrogant and fiercely focused on status, he treats service workers like Janice with condescension. His primary goal is to force his elderly mother out of her college-adjacent home so he can collect a massive payout from the university.

Fiona is a widow and client of Janice's who recently changed careers from an accountant to an undertaker following the sudden loss of her husband. She channels her grief into meticulously wiring and decorating a dollhouse. She worries constantly about her 12-year-old son Adam and struggles to guide him through their shared tragedy.

Mrs. YeahYeahYeah is Tiberius's wife, a snooty woman who insists on treating Janice purely as hired help. She expects Janice to drink cheap instant coffee while keeping the expensive machine for herself. She acts as the initial catalyst for Janice meeting Mrs. B.

Decius is a pedigreed fox terrier belonging to Tiberius and Mrs. YeahYeahYeah. Despite his owners' cold demeanor, Decius is affectionate and lively, making him the sole reason Janice endures cleaning their home.

Adam is Fiona's 12-year-old son. He resists traditional counseling and struggles with grief following the recent loss of his father. He finds unexpected comfort and a renewed sense of connection through spending time with Decius.

Geordie is a famous opera star with a large, warm personality. Originally a young man from Newcastle who walked to London to follow his passion for the opera La Boheme, he is now a successful widower. He treats Janice with genuine kindness, insisting she care for herself while cleaning his home.

Carrie-Louise is a polished, 80-year-old widow who once bravely confronted a street gang, leading to her meeting her future husband. She represents to Janice the ideal of someone who is the confident heroine of her own life story. She relies on Janice to bake treats to pass off as her own during social visits.

Joy is Janice's younger sister who resides in Canada. The two maintain a distant relationship in adulthood, connecting primarily through occasional phone calls. During a past visit, Joy left an enigmatic note indicating she remembers events from their shared, troubled childhood.

Simon is Janice and Mike's 28-year-old son. He grew up attending an expensive private boarding school at his father's insistence. Now a busy professional living in London, he maintains a polite but emotionally distant relationship with his parents, exchanging Christmas cards but rarely visiting.

Mycroft, whose real name is Fred Spink, is a lawyer and an old friend of Mrs. B's late husband. Nicknamed after Sherlock Holmes's brother by Mrs. B, he uses his legal expertise to combat Tiberius's attempts to force Mrs. B out of her house.

Augustus is Mrs. B's deceased husband and the father of Tiberius. He was a former Master at the college and an intelligence operative for MI6. He secured Mrs. B's living arrangement and left her with a lifetime of meaningful mementos.

John is Fiona's late husband and the father of Adam. He worked as a doctor before passing away prior to the events of the narrative. His sudden absence profoundly shapes his family's daily life and emotional state.