Arthur is a middle-aged, gay American novelist who lives in a San Francisco shack. Following the death of his former lover, Robert, Arthur takes a multi-state trip to pay off unexpected back rent. He is prone to social awkwardness, constantly questions his own identity, and worries intensely about his standing in the publishing industry.

Freddy is Arthur's younger boyfriend and the narrator of the story. He is a writer spending time in Maine for a fiction course while Arthur travels. He provides an intimate perspective on Arthur's life while evaluating his own desires for independence, solo travel, and a writing career outside of Arthur's shadow.

Robert is a famous, Pulitzer-prize-winning poet and Arthur's much older ex-boyfriend. He allowed Arthur to live rent-free in his San Francisco shack. His recent death leaves a massive bill of back rent, forcing Arthur out of his comfort zone to save the home.

Mandern is an 85-year-old, notoriously erratic fantasy author. Refusing to fly, he drives a camper van with his dog, Dolly. He enlists Arthur as a travel companion through the Southwest, driven by a personal goal to find his daughter before his health completely fails.

Lawrence is Arthur's long-lost father who fled the family when Arthur was a child to escape the police over a Ponzi scheme. He now lives in the South with his girlfriend. His sudden reappearance forces Arthur to consider the possibility of forgiveness.

Rebecca is Arthur's sister who lives in Delaware. Recently divorced, she suffers from newly developed hand tremors that physically manifest her anxiety. She shares Arthur's complicated feelings regarding their absent father and family history.

Marian is Robert Brownburn's former wife. Despite Arthur's past relationship with her ex-husband, she and Arthur maintain a warm friendship, relying on each other to handle the emotional toll of Robert's memorial service.

Finley is the chair of the esteemed literary prize committee. He serves as Arthur's literary nemesis, famous for pushing arbitrary rules about queer literature and deeply insulting Arthur in the past.

Dorothy is the enthusiastic leader of the Last Word Theatre Troupe. She orchestrates a sensitive musical stage adaptation of Arthur's autobiographical short story, welcoming him into her community.

Thomas is an actor in the Louisiana theater troupe. He demonstrates a sharp understanding of the painful, autobiographical nature of Arthur's story and attempts to form a closer connection with the author.

Dolly is H.H.H. Mandern's loyal dog. She travels across the country, providing silent but steadfast companionship to Arthur during his lonely drives after Mandern leaves the tour.

Rosina is a clunky, old camper van given to Arthur by Mandern. More than just a vehicle, Rosina acts as a reliable shelter and steadfast entity that forces Arthur to travel the country at a deliberate pace.

Lacey is H.H.H. Mandern's estranged daughter. Her father travels across the country specifically to find her and make amends.

Arathusa is a resident of the Ambrogio hippie arts commune in the gorge. She teaches Arthur her personal life philosophy, which he initially finds confusing but eventually adopts.

Vlad is Dorothy's husband and a member of the Southern theater community who helps coordinate the troupe's logistics.

Jason is a sociology professor who wins a bet against his students by going six months without human touch, a streak he breaks during a poignant interaction with Freddy.

Andrew is Arthur's former high school bully who has grown up to become a kindly history and driver's education teacher in Delaware.