Emma is a 31-year-old woman born and raised in Acton, Massachusetts. In her youth, she actively rebels against her family's bookstore business, preferring travel and adventure over staying in her hometown. The tragic disappearance of her first husband forces her to rebuild her life entirely from scratch. She eventually settles down, discovers a delayed love for reading, and accepts a marriage proposal from a new man, only to have her reality upended by a shocking phone call.

Jesse is Emma's first husband. A high school swimming prodigy who secretly despises the sport, he initially bonds with Emma over their shared desire to escape the expectations of their families. He works as a production assistant on nature documentaries, feeding his desire to travel the world. After vanishing in a helicopter crash during an Alaskan work trip, he contacts Emma years later to announce he survived.

Sam is a high school music teacher and Emma's fiancé. Musically talented from a young age, he played multiple instruments and worked at Blair Books during his teenage years. He provides Emma with stability and deep affection when they reconnect in a music store years after the loss of her husband.

Marie is Emma's older sister. Often referred to as the "Bookseller's Daughter" in their youth, she is well-read, popular, and content to follow in her parents' footsteps by working at Blair Books. Her relationship with Emma is initially strained due to their opposing personalities but shifts as they reach adulthood.

Colin is Emma and Marie's father. He runs Blair Books, a local shop started by his uncle in the 1960s. He takes pride in the family business and provides a supportive, if sometimes expectant, environment for his daughters.

Ashley is Emma's mother and co-owner of Blair Books. Alongside her husband, she manages the family business and harbors hopes that her daughters will one day take over the store. She acts as a comforting presence for Emma during periods of intense grief.

Olive is Emma's high school best friend. She encourages Emma to pursue her initial crush on Jesse and remains a steadfast presence in her life through early adulthood and later milestones.

Francine is Jesse's mother. She places intense expectations on her son's competitive swimming career during his youth. When Jesse disappears, she struggles heavily with the trauma and relies on the Blair family for support.

Joe is Jesse's father. He shares his wife's ambitions for Jesse's swimming career and serves as a protective figure for his wife when they face the loss of their son.

Carolyn is the captain of the girls' soccer team. She briefly dates Jesse during high school, causing Emma to temporarily suppress her own feelings for him.

Mike is Marie's partner. He dates her during her college years and later marries her, building a life close to the Blair family in Acton.

Lindsay is Carolyn's older sister. She casually visits the bookstore during Emma's youth, serving as a reminder of Jesse's romantic life outside of Emma.