Hadley is a 17-year-old American adjusting to her parents' recent divorce and her father's impending second wedding. She struggles with claustrophobia and intense anxiety regarding airports, along with an unusual fear of mayonnaise. Reluctantly traveling to London, she wrestles with feelings of betrayal toward her father's permanent relocation to England. She intends to return a book he gave her unread as a form of silent protest.

Oliver is a British student studying at Yale who crosses paths with Hadley at the airport. He projects a chivalrous and easygoing demeanor, offering to help carry her luggage through the crowded terminal. Unlike Hadley, he loves the transitional space of airports and airplanes. He uses the suspension of travel to avoid thinking about his arrival in London, occasionally betraying underlying tension through his body language.

Andrew is a literature professor who originally traveled to Oxford for a teaching semester but ended up relocating to England permanently. He communicates his affection primarily by gifting classic books to his daughter. Though his choices upended his family, he remains eager to include Hadley in his new life.

Kate is Hadley's mother, residing in the United States. She encouraged her ex-husband Andrew to accept the Oxford teaching position that eventually led to their divorce. Despite the dissolution of her marriage, she maintains a pragmatic view of love and serves as Hadley's primary emotional anchor.

Charlotte is Andrew's British fiancée. She is a tall, graceful woman who is eager to build a positive relationship with her soon-to-be stepdaughter. Despite Hadley's initial determination to dislike her, Charlotte remains consistently welcoming and kind.

Harrison is a local dentist who meets Hadley and her mother during a routine appointment. He pursues a serious relationship with Kate Sullivan and makes multiple attempts to propose marriage to her.

Violet is Charlotte's maid of honor. Having experienced her own father's remarriage, she possesses a sympathetic understanding of Hadley's emotional struggles regarding the wedding ceremony.

Oliver's father is a severe man who struggled to show overt affection to his son. His harsh demeanor during Oliver's childhood creates a lasting emotional distance between them, though he occasionally showed care in subtle ways.

Oliver's mother is an English woman whom Oliver feels highly protective of. She occasionally travels to the United States to visit her son at university.

Monty is Charlotte's brother. He participates in the wedding ceremony, acting as Hadley's escort down the aisle at the church.

Mrs. O’Callaghan is a family friend of Charlotte's who attends the wedding ceremony. Her passing comments about travel plans inadvertently provide Hadley with crucial information about the surrounding area.

Mitchell is Hadley's former high school boyfriend. She reflects on their relationship as uncomplicated and somewhat dull compared to the sudden connection she experiences at the airport.