Roseanne is a near-centenarian patient who has spent much of her life in mental institutions. Unsure of her exact age, she relies on her vivid memories of her youth in Sligo, Ireland, to write an account of her life. As a young Protestant woman, she faced intense societal and religious pressures, and she now carefully hides her writings under a floorboard while navigating her daily interactions with the hospital staff.

Dr. Grene is the 65-year-old psychiatrist managing the Roscommon asylum, where he has treated Roseanne for 24 years. Struggling with personal turmoil and an estranged marriage, he maintains a commonplace book to process his thoughts. He approaches his oldest patient with a mix of professional duty and personal fascination, careful not to offend her into silence.

Joe is Roseanne's beloved father, a Presbyterian who works as the superintendent at a Catholic cemetery in Sligo. A former member of the British Merchant Marine, he is a cultured, storytelling laborer who reads old sermons and rides a motorbike. His devotion to his family and his work defines Roseanne's early life.

Tom is a handsome, confident jazz musician from a middle-class Catholic family in Sligo. Playing trumpet and clarinet in his own band, he is an optimistic man eager for upward mobility. His conservative political leanings and religious background frequently clash with Roseanne's Protestant roots and the political turbulence of the era.

Father Gaunt is a stern, powerful Catholic priest in Sligo who wields significant influence over the local community. Dressed in oddly stylish clerical clothing, he is highly invested in maintaining religious and social order. He views Protestantism and female sexuality with deep suspicion, heavily involving himself in the personal affairs of both the Clear and McNulty families.

Cissy is Roseanne's mother, originally a dark-haired chambermaid with striking green eyes. She struggles intensely with the poverty and dreariness of her life in Ireland. Her mysterious sorrow leads to a gradual decline into madness, leaving her emotionally vacant and passive.

Jack is Tom's brother and closest friend, educated in engineering and geology. Having spent time in Africa with the Royal Engineers, he is highly class-conscious and concerned with public appearances. He drives the nicest car in Sligo and uses his education to distance himself from those he views as lower-class.

Eneas is the "black sheep" of the McNulty family, an outcast spoken of largely in whispers by his brothers. A soldier who spends much of his time away from Sligo, he forms an unexpected bond of shared isolation with Roseanne when he returns from the destruction of war.

Mrs. McNulty is Tom's devoutly Catholic, strict, and unsympathetic mother. Dressed entirely in black with a distinctive widow's peak, she prefers self-denial and total submission to the Church. She actively seeks Father Gaunt's counsel and fiercely protects her family's social standing against outsiders she deems unsuitable.

"Old Tom" is Mrs. McNulty's husband and the patriarch of the McNulty family. Working at the Sligo Mental Hospital, he is a relatively joyous man compared to his severe wife. He takes immense satisfaction in his garden and his music, communicating more comfortably through his flute than through direct confrontation.

John is an elderly, sometimes inattentive custodian at Roscommon Regional Medical Hospital. Despite his menial position, his grumbling demeanor, and his perpetually open flies, he takes a quiet, ongoing interest in Roseanne's wellbeing. He lays mouse traps in her room and subtly watches over her.

John is an anti-treaty Republican rebel involved in the Irish Civil War. Driven by the trauma of violence against his family, he operates outside the law and occasionally crosses paths with the Clear family, bringing them into the dangerous political crossfire of the era.

Willie is a seventeen-year-old rebel whose tragic death brings political tensions directly to the cemetery where Joe Clear works. His murder at the hands of soldiers sparks a chain of events that permanently alters the Clear family's standing in Sligo.

Joe is a widower in his fifties who replaces Joe Clear as the superintendent at the Catholic cemetery. Looking to remarry, he sets his sights on young Roseanne with the active encouragement and backing of Father Gaunt.

Bet is Dr. Grene's estranged wife, who suffers from swelling legs and fainting spells. Consumed by a fear of aging, she maintains a vast collection of night creams and books on roses, living quietly in the upper rooms of their home after a rift in their marriage.

Mrs. Prunty is the Quaker owner of the Cafe Cairo in Sligo. She offers Roseanne employment after a memorable encounter on the beach, providing the young woman with a crucial source of income and community following her father's death.