Murray is a 100-year-old former professional baseball player who spent fifteen years playing for the Chicago Cubs. Deeply grieving the loss of his wife, Jenny, he feels out of place in the modern world and struggles to find meaning in his continued existence. He takes a daily pill to prevent fluid from filling his lungs, but is otherwise remarkably healthy for his age. His perspective shifts drastically when he meets a young, terminally ill boy and commits himself to fulfilling the child's remaining wishes.

Jason is a 10-year-old boy suffering from a severe heart condition that requires an eventual transplant. He relies heavily on an oxygen mask and spends much of his time enduring medical treatments or playing video games to escape his reality. To cope with his prognosis, he writes a list of five wishes he wants to accomplish. He speaks using modern slang that often confuses older adults but maintains a resilient and imaginative spirit.

Tiegan is Jason's 10-year-old friend and neighbor. She is highly intelligent, remarkably mature for her age, and deeply knowledgeable about baseball statistics. She shares an affectionate bond with her mother, defined by their shared motto "SBK" (Strong, Brave, Kind). Inspired by Jason's determination, she creates her own distinct list of five wishes.

Father James is the Catholic priest at St. Joseph's who provides spiritual and practical guidance to Murray. He actively assists the elderly man in connecting with Jason by organizing early email communications and coordinating with a formal mentorship program. He serves as a calm, stable presence in Murray's life, offering pragmatic advice on faith and human connection.

Chance is Murray's adult grandson. He attempts to bridge the generational divide by bringing modern technology into his grandfather's home, but his efforts often result in arguments. He harbors fond memories of playing catch with Murray as a child, though his adult life—marked by multiple divorces—causes friction with his grandfather's traditional views.

Benedict is Jason's father. Following a divorce from Jason's mother, he focuses entirely on earning money to pay for his son's expensive medical treatments. This intense focus on financial provision leaves him emotionally distant, and he avoids spending quality time with Jason. He is highly protective of his son and skeptical of outside interference.

Anna is Jason's devoted mother and primary caregiver. She is highly affectionate toward her son, managing his daily medical needs and creating a warm home environment. As a single mother, she sometimes finds herself the target of Jason's misguided attempts to set her up on dates to fulfill his wish list.

Della is Tiegan's mother and Anna's neighbor. She removed herself and her daughter from an abusive situation in the past, leading her to prioritize emotional warmth and resilience in her parenting style. She is deeply affectionate with Tiegan, reinforcing their bond with a personal motto.

Collins (born Jackson Collins) is a young man who works as a model for local art classes. He is respectful and polite, quickly striking up an easy camaraderie with Murray despite the vast age difference between them. He shows a genuine interest in the people he meets.

Dr. Keaton is Murray's long-time physician. He monitors Murray's physical health while remaining highly concerned about his patient's isolation and lack of purpose. He firmly encourages Murray to find social activities, going so far as to suggest modeling work to force him out of the house.

Javier is a young professional baseball player for the Chicago Cubs. He represents the modern era of the sport Murray once played. He generously uses his time and resources to assist fans and support the local community.

Mindy is a high school cheerleader. She becomes the specific object of Jason's first wish, representing his goal to kiss a girl on the lips. She harbors a crush on her school's quarterback, a detail Jason uses to approach her.

Derek is a doctor whom Jason meets at the hospital. Without his mother's knowledge, Jason invites Derek to their house for dinner under false pretenses, attempting to set the two adults up to fulfill a wish on his list.

Jenny was Murray's wife of eighty years who passed away eighteen months before the story begins. Her absence leaves Murray unmoored and longing to join her. Memories of her warmth, kindness, and their life together constantly influence Murray's actions.