Near the beginning of Bud, Not Buddy, Bud is placed in a new foster home. Todd, his new foster brother, treats him badly. Bud decides to run away and go off on his own. He wants to find Mr. Calloway, a jazz band leader who he thinks might be his father. This is the first event in the story.
Bud eventually finds Calloway and his band. The more that he spends time with the band, the more that Bud feels that they are like family to him. Bud has a moment of realization at a fancy restaurant called the Sweet Pea. He realizes how much he loves spending time with the band. The only person who he does not feel a connection with is the grouchy Mr. Calloway. This moment is the second event.
The last event is when Bud finds out that Mr. Calloway is not his father. In fact, the man is his grandfather. Bud is given his own saxophone and becomes a member of the band.