The story opens with Bud being placed with a new foster family, the Amoses. Bud soon meets Todd Amos, their 12-year-old son, who teases him mercilessly and calls him Buddy. After a fight with Todd, Bud is forced to spend the night in the garden shed, where he mistakes a hornet nest for a vampire bat. He slices the nest in half with a rake, upsetting the hornets and getting himself stung. During his adrenaline rush, he breaks through the window of the shed.
After escaping, Bud takes revenge on Todd by making him wet his bed by pouring warm water on Todd, as the Amoses can’t stand bedwetting. He also hides the Amoses’ shotgun and takes leave. He then sleeps under a Christmas tree for the night. The next day, he wakes up to find that he had missed the breakfast line at the mission, but is saved by a couple who pretended he was their son. The next morning, his friend Bugs wakes him up so they can go to the West.
Bud runs away with Bugs to Hooverville where they eat and plan to get on the train leaving West the next day. The train, however, leaves early, and Bud, unlike Bugs, fails to hop on and is left behind. Bud learns about the walking distance from Flint to Grand Rapids from a librarian and starts walking to Grand Rapids, Michigan. On the way, he meets Lefty Lewis —- whom he thought was a vampire as he had a box of blood in his car —- who gives Bud a ride in his car to Grand Rapids to find his father. He stays with Lefty for a short while and meets his daughter's family. He then leaves to find his father, whom he believes is Herman E. Calloway.
Bud meets Herman and his band and declares himself to be Herman's son, though his confidence is shaken when he sees that Herman is elderly. Bud becomes friends with the band members (who give him a saxophone by the end of the book), but Herman treats Bud with great animosity. Bud is soon forced to deliver the news that his mother, Angela Janet, is dead. This brings great grief to Herman, who is revealed to be Angela's estranged father.
The story ends with Herman apologizing to Bud for his animosity and allowing him to stay with him and the band. Despite all of his dilemmas and grief, Bud had a happy ending.
