The third scene establishes the relationship between Tom and his half brother, Sid, a boy as unlike Tom as one can possibly imagine. Tom is the typical "bad boy" of Sunday school lessons who doesn't mind his elders, skips school, and plays tricks on people. Sid is the insipid "good boy" who minds all his elders and does everything expected of him. Sid delights in being a tattletale, in being a prig, and in getting Tom into trouble.
The fourth scene involves Tom's asserting his own turf in the presence of a newcomer, Alfred Temple. The "darings" (I dare you to el ) and the verbal sparrings lead to a fist fight that Tom wins. Tom is further contrasted to the well-dressed new boy because Tom fights fair while the new boy, when Tom turns his back, cowardly throws a stone and hits Tom.
In short, this first chapter firmly establishes Tom's relationship with his world: He is a child, doing things a child would do. He lives in a slave state. He has no parents, but has a loving, parent figure. And he is mischievous but good-natured.
