After Umuaro provokes a war with Okperi, the British colonial administration steps in to stop the fighting. They rule in favor of Okperi, based in part because of testimony of Ezeulu, the Chief Priest of Ulu and a resident of Umuaro.
Umuaro is angry with Ezeulu for siding with Okperi. They accuse him of bringing the white man into Umuaro, despite the fact that Ezeulu had originally opposed the war with Okperi. Nwaka challenges Ulu, suggesting that he's an impotent god, and he might be replaced him with a new god. Nwaka spreads stories about Ezeulu, suggesting he's power hungry and is angling to be the king of Umuaro. Nwaka aided by Ezidemili, the priest of the lesser deity Idemili, who owns the sacred python. Over the course of several years, the enmity between Ezeulu and Nwaka grows, until it infects both of their villages.
A few years after the war, Ezeulu sends his son to learn the ways of Christianity. Oduche takes to the new religion, learning theology and admiring the catechist. He wants to be accepted into this community. So when the new catechist suggests that he must prove his faith by confronting old religious beliefs and killing the sacred python, Oduche decides to do just that. He chickens out at the last minute, and puts the sacred python in his box, hoping it will die, but he won't be responsible for killing it. When Ezidemili, the priest of Idemili (the deity that owns the python), hears of it, he sends Ezeulu a message. Ezidemili wants to know what Ezeulu intends to do to purify his house. Ezeulu ups the ante, responding that Ezidemili can take a hike, and the animosity between the two villages continues to grow.
Winterbottom is forced to comply with British colonial rule, and must appoint a warrant chief for Umuaro. He decides that Ezeulu is just the man, the one honest man he knows in Umuaro. But Ezeulu is reluctant to leave Umuaro when Winterbottom's messengers call, and Winterbottom gets ill while Ezeulu thinks about what he should do. Ezeulu asks his village elders for advice, and they all say he should go to Winterbottom, emphasizing that he's at fault for the white man's presence in their midst. When Ezeulu arrives, Clarke detains him, deciding to teach Ezeulu a lesson. Then Ezeulu refuses the warrant chief position, and Clarke detains him until he has learned to be more "cooperative" (Winterbottom's words). Finally, with no real reason to detain him longer, and with orders from above to forget the warrant chief business, Clarke lets Ezeulu go home.
Ezeulu is angry that the people of Umuaro have treated him, the chief priest of Ulu, with so little respect, allowing him to be detained by the white man and blaming him for the British presence. Ezeulu decides that he is Ulu's arrow of punishment. Ulu's revenge begins soon after Ezeulu returns to Umuaro.
When Ezeulu's assistants come to ask him why he hasn't called the Festival of the New Yam, Ezeulu says that the time hasn't yet arrived. The elders call on him. Nobody can harvest the yams until Ezeulu calls the Feast. Ezeulu explains that because he was imprisoned in Okperi for so long, and because nobody visited with Ulu during his absence, there are still three sacred yams left. It will take three months before he can call the Feast of the New Yam.
Though the men plead with him that they will take the punishment on their own heads, Ezeulu refuses. It is his duty to keep the tradition exactly as it is, and he can't eat more than one sacred yam in any given month. The village of Umuaro grows desperate as they hear that Ezeulu plans to stubbornly wait the three months out, knowing that they will begin to starve and their crops will be ruined if they can't harvest.
After a couple of months of famine, the people of Umuaro are suffering. The catechist at the Christian church, John Goodcountry, offers to accept the people's sacrifice of new yams so that they can harvest their crops. He says that the Christian god will protect them from Ulu's wrath. When Ezeulu's son Obika dies suddenly after performing a funeral rite, the people decide that it is Ulu's punishment on his headstrong and stubborn priest.
When the people of Umuaro realize that Ulu has punished its priest, Ezeulu, they turn their sights to another god. They ask the Christian god for protection from Ulu's wrath. They plant that year's crops in the name of Christianity.