Maniac Magee lost both his parents in a trolly accident. He went to live with his aunt and uncle, Dot and Dan. The couple could not get along, and the tension in the house eventually led to Maniac running away. In the town where Maniac goes, segregation exists. The white people live on one side of the town, and the black people live on the other. Maniac doesn’t care. He just wants a family, and when he is asked to stay in his new friend Amanda Beale's home, he is happy. However, he soon experiences prejudice from the boys in the neighborhood. He does not want the family he has been staying with to suffer, so he leaves.
Maniac begins sleeping at the zoo where an elderly man, Grayson, discovers him. He moves in with the man, and together they become a family. Maniac is excited to have an address to call home. The man passes away, and Maniac is again in search of a home. A white family accepts him. However, he puts the relationship at risk when he invites Mars Bar, a black boy, to a birthday party in the white neighborhood. When Mars Bar saves a child from the trestle, the boy learns about Maniac’s family’s death. Maniac moves back in with the Beales family and is accepted in the neighborhood and as a member of their family.
Maniac is finally happy when he has an address of his own and a place to call home with a family that wants him.