Joy Davidman is a Jewish American writer and mother of two living in upstate New York. Raised in the Bronx by strict Ukrainian immigrant parents, she carries a lifelong intellectual curiosity. As she balances her domestic duties with her writing career, she experiences deep frustration in her turbulent marriage. Seeking answers to her growing spiritual questions, she initiates a correspondence with an English author that shifts her worldview.

C. S. Lewis, known to his friends as Jack, is an esteemed English author, Christian apologist, and professor at Oxford University. He converted to Christianity from atheism years earlier, allowing him to offer spiritual vocabulary to those exploring faith. He lives at his family home, the Kilns, and participates in an informal group of academics known as the Inklings.

Bill is Joy's husband and the author of the successful novel Nightmare Alley. Originating from Baltimore, he possesses a Southern charm but struggles heavily with alcohol addiction and infidelity. He desires a traditional, submissive wife who manages the household, which causes severe friction with Joy's ambitions as a writer.

Renee is Joy's cousin, originally from Mobile, Alabama. Having grown up as the favorite of Joy's mother, Renee embodies traditional manners and domestic skills. She moves into the upstate New York farmhouse with her children to escape her abusive ex-husband, taking over many of the household chores.

Warnie is Jack's brother, sharing the family home in Oxford. Like Bill, he faces personal battles with alcohol, but he approaches his struggles with vulnerability and warmth. He acts as a steadfast companion to his brother and openly welcomes new friends into their home.

Davy Gresham is Joy and Bill's son. He wears glasses, is highly inquisitive, and harbors a deep fascination with astronomy. He frequently engages in deep emotional discussions with his mother and enjoys reading complex books, including French editions of fantasy novels.

Douglas Gresham is Joy and Bill's younger son. He shares a tight bond with his brother and mother, finding an escape in the stories his mother reads to them. He observes the tension in his parents' marriage while trying to find normalcy in his childhood.

Florence Williams, affectionately nicknamed Michal, is the widow of the poet and Inkling Charles Williams. She quickly befriends Joy upon her arrival in London, introducing her to new literary circles and sharing the common pain of dealing with an unfaithful husband's legacy.

Belle is Joy's former college roommate from Hunter College. She holds a master's degree from Columbia and shares Joy's early literary ambitions. Belle acts as a long-time confidante who supports Joy through her shifting political beliefs and marital difficulties.

Phyl Williams is an attractive and charming friend of Joy and Bill. She lives in London and offers Joy a place to stay, reciprocates the hospitality Joy showed her during a previous personal crisis in New York.

J. R. R. Tolkien is an esteemed professor at Oxford and a prominent member of the Inklings. Nicknamed Tollers, he holds traditional views regarding gender and academia. He appears brusque and skeptical when faced with Joy's outspoken American demeanor.

Chad Walsh is a college professor and writer who previously authored a profile on C. S. Lewis. He establishes a spiritual and intellectual friendship with Joy, encouraging her to focus her religious devotion on God rather than earthly mentors.

Eva Walsh is Chad's wife and a supportive friend to Joy. During their summer visits, she listens to Joy's frustrations regarding motherhood and writing, offering encouragement when Bill harshly critiques Joy's work.

Claude is Renee's abusive ex-husband who lives in Mobile, Alabama. His violent behavior prompts Renee to flee with her children and seek refuge at Joy and Bill's farmhouse in upstate New York.

Howie is Joy's younger brother. As children living in the Bronx, he sneaks out at night with Joy to visit the caged lions at the zoo. As adults, they experience an estrangement after Joy publishes an autobiographical piece detailing their family history.

Mrs. Miller is the housekeeper at the Kilns, the Lewis family home in Oxford. She manages the domestic duties for Jack and Warnie, maintaining the household where Joy eventually finds refuge.

George Sayers is a former student of Jack who now teaches at Malvern. He joins Jack in greeting Joy and Phyl during their first in-person meeting, participating in their early conversations about England and academia.

Dorothy Heyward is the wife of the author whose novel inspired the play Porgy and Bess. She meets with Joy in London, sharing stories about her involvement in adapting her husband's work for the stage.

Mrs. Bagley is Joy's landlord in London. When Joy struggles to pay for her current rooms, Mrs. Bagley demonstrates compassion by offering her more suitable accommodations for less money, easing her financial burden.

Father Bide is a priest and a friend of Jack. When the local bishop refuses to grant an exception for Joy and Jack to marry in the Church, Father Bide steps in to perform the ceremony and pray for Joy in her hospital room.

Kay is a friend of Joy who lives nearby. When Joy falls and breaks her leg due to her spreading illness, Kay and her husband rush to the house to provide immediate medical help and comfort.