At 9:30, his appointed bedtime, Tom drifts off to sleep. Outside his window, Huck meows—their secret call. It takes full-blown howling to wake Tom.
Tom had promised Huck not to fall asleep before he came. Even though he shares a spirit of companionship among other boys, Tom can't be bothered to obey anyone.
They head to the graveyard with Huck's dead cat, spooked by the idea of ghosts.
The boys go to the graveyard because it's the most dreadful place they can think of. A large part of the hold their superstitious beliefs have over them is that they are so thrilling.
As they play in the graveyard, they notice three approaching figures, and hide. The figures turn out to be Dr. Robinson, Injun Joe, and Muff Potter. The hiding boys look on as the three begin grave-digging.
The three men are breaking the law in digging up the graves of the dead. Though Tom and Huck were originally afraid of encountering ghosts, real criminals are far more scary.
The three men argue after Injun Joe demands more payment from Dr. Robinson for the corpse they've dug up. He wants revenge for the doctor's insulting him when he begged for food five years earlier. A fight breaks out. Muff takes Injun Joe's side. Dr. Robinson knocks Muff out with a gravestone. Injun Joe stabs Dr. Robinson with Muff's dropped knife.
Up until the murder, the novel largely describes the fanciful games of Tom and his friends. The murder signifies that a harsher reality has set in. These men are not the heroic figures that Tom and Joe imagined outlaws to be in the woods earlier that day. They are petty, backstabbing, and drunken. Notably, Injun Joe, the "half-breed," is the truly evil character in the group, suggesting racial prejudice on Twain's part against Native Americans.
Injun Joe plants Muff's knife on the body of Dr. Robinson, then steals Robinson's valuables. When Muff regains consciousness, Injun Joe says Muff killed Dr. Robinson. Muff blames his drunkenness. Injun Joe promises he won't turn him in, and Muff runs away, forgetting his knife.
The boys look on as the behaviors of adults who lie to one another and drink too much take on real consequences. Though Tom has fantasized about fighting as an outlaw and even the tragedy of his own death, witnessing an actual stabbing reveals the event to be disturbing and inglorious.