Bud is a ten-year-old orphan living in Flint, Michigan during the Great Depression. He carries a battered suitcase containing a few precious mementos, including a photograph of his mother and flyers for a jazz band. Convinced that the bandleader on the flyers is his father, he decides to flee the foster care system to search for him. He maintains a running mental list of rules to help him survive and interpret adult behavior.

Bud's mother passed away when he was six years old, leaving him to the orphanage system. She is remembered as an energetic, intense woman who offered Bud important life advice about closed doors opening. She kept several flyers for a jazz band, which drives Bud's quest to find the man he believes is his father.

Mr. Lewis is a railroad porter and grandfather who finds Bud walking along the road at night. He is involved in organizing a labor union for Pullman porters and safely transports blood to the hospital. He provides Bud with food, shelter, and transportation to Grand Rapids.

Herman is an older, successful jazz musician who leads a band called the Dusky Devastators of the Depression. He is strict with his band members and highly protective of his privacy. Bud travels to Grand Rapids under the firm belief that Herman is his long-lost father.

Mr. and Mrs. Amos are a strict foster family who take Bud in from the orphanage. They prioritize their biological son's word over Bud's and use severe punishments, such as locking Bud in a dark shed. Their treatment convinces Bud to run away from the foster system entirely.

Todd is the twelve-year-old biological son of the Amos family. He is much larger than Bud and uses his size to bully foster children. He is a skilled liar who easily convinces his parents that Bud started their physical altercation.

Bugs is a fellow orphan and Bud's best friend from the Home. He earned his nickname after a cockroach crawled into his ear, requiring a hospital visit to remove it. He decides to run away and hop a freight train west to find migrant work, inviting Bud to join him.

Deza is a young girl living in the shantytown with her family while her father seeks employment. She shares a conversation with Bud about carrying family inside one's heart rather than in a suitcase. She also shares a brief kiss with Bud before he attempts to catch the train.

Eddie is the saxophone player for Herman E. Calloway's band. He is quick to make Bud feel welcome and offers him practical advice about surviving the band's strict rules. He gifts Bud an old saxophone case to replace his tattered suitcase.

Miss Thomas is the talented vocal soloist for the jazz band. She immediately steps into a maternal role upon meeting Bud, noticing his injuries and ensuring he is fed. She acts as a buffer between Bud's sudden arrival and Mr. Calloway's hostile reaction.

The musicians making up Herman E. Calloway's band travel together to perform during the Great Depression. The group operates under strict rehearsal rules set by their leader. They adopt Bud into their routine and give him a musician nickname.

Mr. Jimmy is the horn player for the jazz band. He is practical and acts as an investigator when Bud first claims a connection to Mr. Calloway, offering the hungry boy a meal in exchange for the truth about his journey.

Doug is the drummer for the jazz band. He possesses a mischievous sense of humor and attempts to trick Bud into giving Mr. Calloway an overly affectionate greeting, though Bud recognizes the prank.

Roy is the piano player and the only white member of the band. Because Black people face severe property ownership restrictions in the area, Roy's name is legally used on the deed to the Log Cabin club.

Mrs. Sleet is Mr. Lewis's daughter who lives in Flint. She opens her home to Bud, providing him with a comfortable bed and a chaotic but loving family breakfast that contrasts sharply with the silent meals at the orphanage.

Jerry is a six-year-old orphan who is assigned to a new foster home with three older girls. He is terrified of the change, prompting Bud to offer him comfort and reassurance despite Bud's own anxiety.

Miss Hill is a librarian who was previously kind to Bud and his mother. Bud hopes to find her for assistance after running away, but he learns she has recently married and moved to Chicago.