Isaac Okonkwo has a religious discussion with some of the merry-makers celebrating the return of Obi after four years in England.
Isaac claims that rainmaking ceremonies are useless, and that rainmakers do not have the power to prevent lightning from striking people. He says that it is the work of God that no person in Umuofia has been killed by lightning. (The word for thunder exists in Igbo, so it's hard to know if Achebe was making a joke here or if he just used the wrong word.)
The merry-makers want to break a kola nut, but Isaac insists they use kola nut that hasn't been sacrificed to idols since his is a Christian house.
When one of the men claims that Obi is the reincarnation of his grandfather, Isaac claims that dead men do not return.
Obi and his father talk, and Isaac asks Obi if he had time to read the Bible in England. Obi says he did, but it was in English.
When Obi returns for a visit at Isaac's request, Isaac is clearly dismayed that Obi is dating an osu.
Isaac says Obi doesn't realize the depth of what he wants to do, and that he will be bringing a curse upon his family, and upon his children.
Isaac listens to Obi's arguments but tells him that osu is like leprosy. You can marry a leper, but you can't expect people to agree to it. The stigma is too strong.
The next day, Isaac reminds Obi of all that he had given up in order to become a Christian. He explains that his father cursed him, which is a terrible thing to do to a child. He tells Obi that because he went through fire to be a Christian, he understands what it means to be a Christian more than Obi ever can.