Bud Caldwell is a ten-year-old boy who lives in a home for orphans.  His mother died when he was six-years-old.  When the book begins, Bud has already lived with two foster families since he lost his mother.  In the first chapter, he is selected to be placed with another foster family.  

Bud isn't quite sure who his biological father is.  He has a flyer which his mother kept of a jazz band player.  He thinks that this man, Mr. Calloway, might be his father.

Unhappy with his new foster family, Bud runs away.  He decides to seek out the man that might be his father.  Bud goes on a long journey of self discovery before realizing that Mr. Calloway is his grandfather and not his father.  He also finds an adopted family in the band.