So, it's been four years since his mom died, and ten-year-old Bud Caldwell takes off from his third foster home in search of a better way to live his life. He's sick of being an orphan: unwanted, unloved, and all alone. On his own, he finds out how rough it is in Michigan in 1936, during the Great Depression. He meets many kind people along the way who help him complete his most awesome quest: to find the man that he thinks is his father. He's looking for a guy whose picture was on some old flyers for jazz concerts his mother kept around their house, so he doesn't have too much to go on. Oh, and did we mention that Bud is looking for a place to finally call home? Sounds pretty tough, right?
Bud thinks not.
So, Bud meets up with Bugs, a boy from the home, and together they go to Hooverville, the shanty town in Flint, in order to hop a train to California to get jobs. At the shantytown, Bud meets Deza Malone, who turns out to be a good friend. When Bud misses the train, he goes back to Flint, and a nice librarian helps him figure out how to get to Grand Rapids, where Calloway lives. On his hike to faraway Grand Rapids, Bud meets Lefty Lewis, who picks him up by bribing him with food. Bud gets to sleep in a real bed at Lefty's daughter's house, and Lefty gives Bud a lift to the Rapids.
In Grand Rapids, Bud confronts his father and his father's jazz band. Dear old dad, unfortunately, doesn't want much to do with poor Bud, but the other band members are nicer and invite Bud to dinner. Eventually, Bud finds a family among the jazz band and their rich and famous leader, who turns out to be his grandfather.
In the end, Bud is happy at home in Calloway's house, and the book ends with Bud learning to play the new saxophone his buddy Steady Eddie bought for him.