Gretel is a 91-year-old woman living comfortably in the upscale Winterville Court in London. Originally from Germany, she spends her older years seeking a quiet, ordered life while keeping her deep historical ties hidden. Decades earlier, she and her mother changed their names and relocated to Paris to escape the immediate aftermath of World War II. She balances a dry wit and independence with an enduring, guarded privacy regarding her family's dark legacy.

Alexander is a prominent, wealthy film producer who relocates his family to London for work. He projects a charming, polished exterior but strictly controls the lives of his wife and son. His domineering presence quickly disrupts the quiet atmosphere of the apartment building, drawing the wary attention of those around him.

Kurt is a young, handsome lieutenant who serves as an assistant to Gretel's father during the war. He embodies authority and obedience to the regime, drawing the romantic attention of a young Gretel. Years later, he surfaces in Australia working for a bank under the new surname Kozel.

Heidi is a 69-year-old lifelong resident of Winterville Court who lives across the hall from Gretel. She experiences a degenerative mental condition that makes her memory hazy and sometimes causes her to speak without a filter. She relies heavily on Gretel's companionship to avoid being taken advantage of by opportunistic relatives and scammers.

Nathalie is Gretel's mother, formerly a high-status woman who changes her name and flees to France to escape association with her husband's actions. Struggling to cope with her drastically reduced circumstances, she turns heavily to alcohol. She fixates on finding a wealthy man to restore her respectability and stubbornly clings to her fabricated identity.

Edgar is an aspiring academic who eventually becomes a renowned historian specializing in World War II. During his youth in London, he is a friendly, persistent man who enjoys spending time with friends and attending cultural events. He holds an enduring fascination with history that heavily influences his personal and professional life.

David is a popular, charismatic assistant manager at the London department store where Gretel works. He is fun-loving, open-minded, and encourages Gretel to enjoy life and attend concerts and plays with him. Beneath his carefree exterior, he carries deep personal losses from his family's experiences in former Czechoslovakia.

He is a high-ranking Nazi officer and the commander of the Auschwitz concentration camp. He believes firmly in the regime's ideology and views his devastating work as a professional duty. His legacy hangs heavily over his wife and daughter, dictating their need to hide for decades after his execution.

Eleanor is a highly capable heart surgeon and the soon-to-be fourth wife of Gretel's son, Caden. She maintains strict health routines, regularly tracking her steps and focusing on fitness. Despite Gretel's initial skepticism about the marriage's longevity, Eleanor proves to be an empathetic listener and a sharp observer.

Caden is Gretel's adult son, an entrepreneur who frequently struggles with business solvency and alimony payments. He is anxious about money and regularly pressures his mother to downsize and move into a retirement village. He balances his financial anxiety with a genial demeanor that makes him well-liked by his romantic partners.

Oberon is Heidi's grandson who plans to relocate to Mosman, an affluent suburb in Sydney, Australia. He aggressively attempts to persuade his grandmother to sell her lifelong home to fund his move, framing the scheme as an opportunity to care for her abroad.

Henry is the nine-year-old son of the new downstairs neighbors. Small for his age, bookish, and extremely polite, he prefers reading adventure novels over interacting with his volatile parents. His presence in the building evokes intense, panicked memories for Gretel.

Madelyn is a former actress and the glamorous but deeply troubled wife of Alexander. She spends her days in the apartment, dealing with exhaustion, random emotional outbursts, and a reliance on medication. She finds herself entirely isolated by her husband's strict control over her career and social life.

Cait is a tall, independent Irish bartender who escapes a traumatic family background to start fresh in Sydney. She is observant, quick-witted, and immediately senses that Gretel is hiding a significant past. The two form a pragmatic living arrangement, bonding over their shared desire to build new lives away from Europe.

Émile is a sixteen-year-old French boy working reluctantly in his father's store. He is deeply angry about the losses his family suffered during the Nazi occupation of Paris, particularly the death of his older brother. He catches the eye of a teenage Gretel, who views him as a path to independence.

Rémy is an ostentatious French man who courts Gretel's mother in 1946. He dresses well, wears an eye patch from his time in the war, and frequently makes dramatic promises. He uses his charm to embed himself in Nathalie and Gretel's lives, holding strong allegiances to the French Resistance.

Shmuel is a nine-year-old Jewish boy forced into a concentration camp. He wears a striped uniform with a star and relies on his small fingers to clean bullet shells. He is a quiet, scared child trying to survive in unimaginable conditions.

Bruno is Gretel's younger brother, a curious nine-year-old boy who aspires to be an explorer. He loves reading adventure novels and frequently wanders around his family's properties, seeking to understand the strange environment his father manages. His memory haunts Gretel throughout her entire life.

Hugo is Kurt's young son in Australia. He is an innocent, energetic boy who dreams of becoming an explorer like Captain Cook. He remains entirely unaware of his father's history or the danger his father's past brings to their doorstep.

Cynthia is Kurt's Australian wife. She is a polite, hospitable woman from Melbourne who believes her husband's fabricated past as a conscientious objector from Prague. She values moving forward and frequently voices her frustration with people holding onto old grudges.