"The history of a kid is one part fact, two parts legend, and three parts snowball."

When Jeffrey Magee's parents die in a tragic trolley accident, he is sent to live with an aunt and uncle who hate each other. After eight years of living in a divided home, Jeffrey Magee runs away. One year later he winds up in Two Mills where he amazes everyone with his incredible stunts, earning him the nickname "Maniac."

Two Mills is a town divided by race. The white people live on the west side of Hector Street, and the black people live on the east side. But Maniac, who is white, doesn't recognize the barrier. He quickly befriends a black girl and soon finds himself invited to live with the Beales, a family on the East End.

Maniac seems to have found a warm, loving home at last, but there are some on the East End who do not want a white boy living among them. Because he fears what might happen to the Beales, Maniac runs away again.

When Earl Grayson discovers Maniac living in the buffalo pen at the Elmwood Park Zoo, he takes him into his care. Grayson is a park worker, but Maniac quickly discovers that Grayson was once a pitcher in the minor leagues. As Grayson shares tales of his short-lived baseball career, he also reveals to Maniac that he cannot read. With patience and encouragement, Maniac begins to help the old man learn to read. It seems that Maniac has found a new home living in the equipment room at the park's band shell, but the unexpected death of the old man sends Maniac on the run and deep into despair.

A chance encounter with two young runaways brings Maniac back to the West End of Two Mills and the dysfunctional McNab home. There he sees the terrible effects of the racial barrier in Two Mills, and in his own small way, Maniac decides to make a difference.