Harold is a 65-year-old retired brewery worker living a stagnant, quiet life in Kingsbridge. He decides to walk over 600 miles to Berwick-upon-Tweed in his yachting shoes after receiving a letter from an old friend. Plagued by feelings of inadequacy stemming from a difficult childhood and a strained marriage, he hopes his spontaneous pilgrimage will keep his friend alive.

Maureen is Harold's wife of 45 years who spends her days meticulously cleaning her pristine home and avoiding her neighbors. Harboring deep-seated bitterness and anger over past family events, she sleeps in a separate bedroom from Harold. She views his sudden decision to walk across the country as ridiculous and struggles to understand his motivations.

Queenie is a former finance department worker at the brewery where Harold was employed. Now residing in St. Bernadine's Hospice, she initiates contact with Harold after 20 years of silence. Plain-dressing, highly competent, and possessing a quirky sense of humor, she previously faced sexism from male colleagues but found a steady friend in Harold.

David is Harold and Maureen's intelligent but emotionally troubled son. Struggling to find his place in the world, he is often contemptuous and at odds with his father while maintaining a closer, more protective dynamic with his mother. His battles with depression and substance abuse create a heavy presence over the Fry household.

Rex is the Frys' recently widowed neighbor in Kingsbridge. Mourning the loss of his wife, Elizabeth, he tries to maintain social ties with his reclusive neighbors. He provides a listening ear and gentle friendship to Maureen when she begins to venture outside her self-imposed isolation.

Garage Girl is a young gas station attendant with a wan face and dirty hair. She shares a personal story about her aunt's illness with Harold, introducing him to the idea that having faith can make a difference in someone's life. Her words become the catalyst for Harold's entire pilgrimage.

Martina is a Slovakian immigrant who trained as a doctor in her home country but works as a cleaner in England. She takes Harold into her home when his leg injury becomes severe, tending to his blistered feet and offering him a safe place to rest.

Wilf is a thin, troubled young man struggling with substance abuse who latches onto Harold's pilgrimage. Exhibiting erratic behavior and night terrors, he seeks stability and direction, reminding Harold heavily of his own son.

Rich is an unemployed man separated from his wife who joins the pilgrimage and quickly assumes a leadership role over the group. He attempts to commercialize the walk by creating clothing and pitching a fruit energy drink, compromising Harold's quiet mission.

Kate is a woman who joins Harold's followers while separated from her husband. She frequently clashes with Rich over the route and group decisions, eventually becoming one of the few followers to genuinely listen to Harold's personal struggles.

Napier is the egotistical and pompous manager at the Kingsbridge brewery. Currently on his third marriage, he treats his female employees poorly and proudly displays a collection of crystal clowns in his office.

Joan is Harold's mother, who abandoned the family when Harold was a teenager. She occasionally sent letters filled with misspelled words claiming she was not good at being a mother, leaving a lasting emotional scar on her son.

Harold's father is an alcoholic who raised Harold after Joan's departure. He frequently brought home different women he told Harold to call "Auntie" and ultimately kicked Harold out of the house when the boy turned sixteen.

The Silver-Haired Gentleman is a well-dressed man who strikes up a conversation with Harold over tea cakes. He confides in Harold about his secret younger male lover and his hesitation to buy the man new shoes, demonstrating how strangers feel comfortable sharing their burdens with Harold.

Dog is a stray animal that stubbornly follows Harold's pilgrimage despite Harold's initial attempts to shoo it away. The dog becomes a quiet, steady companion for Harold, especially after he separates from the larger group of pilgrims.

The Very Famous Actor is a celebrity signing books for a large crowd in Bath. Despite his public adoration, he privately struggles with drug addiction and a cynical, jaded outlook on life, reminding Harold heavily of his own son's troubles.

The Oncologist is a medical professional who engages Harold in conversation while taking a break from the heat. After hearing about Queenie and reading her letter, he points out clinical realities about her condition that temporarily plunge Harold into severe depression.

Elizabeth is Rex's recently deceased wife who died from a brain tumor six months prior to Harold's retirement. Her passing leaves Rex lonely and eager to connect with his neighbors.

Philomena is a kind nun working at St. Bernadine's Hospice in Berwick-on-Tweed. She helps care for Queenie and leads Harold in to see his friend at the conclusion of his journey.