In chapter 6 of The Adventures of Tom Sawyer by Mark Twain, Tom meets up with Huckleberry Finn on his way to school. They talk about different ways to get rid of warts. Huckleberry is carrying a dead cat, and he says that he plans to take it to the graveyard at midnight. According to Huck, when some devils come to take the soul of an evil person, the cat will follow the devils and the warts will follow the cat.
In chapter 9, Tom sneaks out of his house shortly before midnight and accompanies Huck to the graveyard. In the graveyard, Tom and Huck find Muff Potter, Doctor Robinson, and Injun Joe talking to each other. They're digging up a grave, and they get to fighting about payment. The doctor knocks down Potter with a gravestone, and then Injun Joe stabs the doctor with Potter's knife and kills him. Injun Joe then puts the knife in Potter's hand, as if Potter has committed the murder.
In chapter 10, Tom and Huck run away to the old tannery. Because they are afraid that Injun Joe will kill them too, they swear a blood oath that they won't tell anybody what they saw in the graveyard.