Part Two of Lee's novel is almost exclusively about the trial and its tensions. The night before the trial is to begin, Atticus guards the door, because there is a very real possibilty that a mob may try to wrest him from the prison and hang him. Atticus' instincts are right. During that long night, carloads of men come by and demand Attitcus hand Tom over. Atticus refuses and Scout shames one of the men by mentioning the debt he owes to her father.
When the trial begins, the blacks are relegated to the balcony (Jem and Scout sneak in up there too, to watch). Atticus presents evidence that Tom could not possibly have held Mayella down and raped her because he has a lame arm. Tom claims that Mayella tried to seduce him and he refused. Atticus contends that the Ewell's have made up the story because of their shame that Mayella would have wanted to sleep with a black man.
Despite the evidence, Tom is conviced anyway, to the joy of the crowd and the sorrow of Atticus and his children.