The village begins to stir with excitement as Muff Potters' trial approaches. However, Tom's conscience nags at him for not clearing Muff's name.
Despite all of Tom's dreams of being a hero, he is too scared to do the right thing..
He approaches Huck to make sure that Huck hasn't told anyone what they saw. Huck responds that Injun Joe would have killed them already if he had. They discuss how Muff doesn't deserve the terrible things being said about him, for he's only a kind old drunk.
Huck's struggle with his conscience is similar to Tom's, but they reassure themselves with the cowardly logic that they'll be murdered too if they speak out against Injun Joe. They fail to act like the brave heroes they often imagine themselves to be.
To console themselves, they do what they can to comfort Muff, sneaking tobacco and matches through the window grate of Muff's cell. Muff praises them for their virtue in remembering how he used to fix their kites and show them where to fish. He warns them never to drink alcohol. Finally, he begs to touch their hands and faces through the grate. They head home overwhelmed with guilt.
On the day that the verdict is to be delivered, the whole village assembles at the courthouse to listen to the final witnesses testify against Muff. They are shocked when Muff's lawyer does not call Muff himself to the stand and chooses not to cross-examine any of the witnesses. The audience assumes the defense lawyer is not making a proper effort.
The villagers have been gossiping for months about Muff's villainy, but they condemn his lawyer for not making an effort to clear his name. Even if they don't act properly, they still expect others to do so. This is the same irony the boys so often face in being scolded by their imperfect elders.
Muff's lawyer finally does speak, saying that he takes back Muff's initial guilty plea. In the shocked courthouse, he calls Tom to the stand. Shyly at first, but then more clearly as he goes on, Tom recounts how he saw Injun Joe stab Dr. Robinson.
Tom has made the right moral decision, and, unlike on Examination Night when he couldn't stand the glare of the crowd's attention, now, truly acting as the hero he has always wanted to be, he is unfazed.
At the climax of Tom's story, Injun Joe leaps out the window and escapes.
Twain's chapter about Tom's taking on an adult's responsibility ends with a wholly unrealistic dramatic escape, much like one Tom would concoct while playing with other boys. The novel could have ended with Tom saving Muff's life and thus becoming an adult, but the heart of the novel is ultimately in enjoying tales of boyhood mischief and adventure..