Things Fall Apart is about the tragic fall of the protagonist, Okonkwo, and the Igbo culture. Okonkwo is a respected and influential leader within the Igbo community of Umuofia in eastern Nigeria. He first earns personal fame and distinction, and brings honor to his village, when he defeats Amalinze the Cat in a wrestling contest. Okonkwo determines to gain titles for himself and become a powerful and wealthy man in spite of his father's weaknesses.
Okonkwo's father, Unoka, was a lazy and wasteful man. He often borrowed money and then squandered it on palm-wine and merrymaking with friends. Consequently, his wife and children often went hungry. Within the community, Unoka was considered a failure and a laughingstock. He was referred to as agbala, one who resembles the weakness of a woman and has no property. Unoka died a shameful death and left numerous debts.
Okonkwo despises and resents his father's gentle and idle ways. He resolves to overcome the shame that he feels as a result of his father's weaknesses by being what he considers to be "manly"; therefore, he dominates his wives and children by being insensitive and controlling.
Because Okonkwo is a leader of his community, he is asked to care for a young boy named Ikemefuna, who is given to the village as a peace offering by neighboring Mbaino to avoid war with Umuofia. Ikemefuna befriends Okonkwo's son, Nwoye, and Okonkwo becomes inwardly fond of the boy.
Over the years, Okonkwo becomes an extremely volatile man; he is apt to explode at the slightest provocation. He violates the Week of Peace when he beats his youngest wife, Ojiugo, because she went to braid her hair at a friend's house and forgot to prepare the afternoon meal and feed her children. Later, he severely beats and shoots a gun at his second wife, Ekwefi, because she took leaves from his banana plant to wrap food for the Feast of the New Yam.
After the coming of the locusts, Ogbuefi Ezeuder, the oldest man in the village, relays to Okonkwo a message from the Oracle. The Oracle says that Ikemefuna must be killed as part of the retribution for the Umuofian woman killed three years earlier in Mbaino. He tells Okonkwo not to partake in the murder, but Okonkwo doesn't listen. He feels that not participating would be a sign of weakness. Consequently, Okonkwo kills Ikemefuna with his machete. Nwoye realizes that his father has murdered Ikemefuna and begins to distance himself from his father and the clansmen.
Okonkwo becomes depressed after killing Ikemefuna, so he visits his best friend, Obierika, who disapproves of his role in Ikemefuna's killing. Obierika says that Okonkwo's act will upset the Earth and the earth goddess will seek revenge. After discussing Ikemefuna's death with Obierika, Okonkwo is finally able to sleep restfully, but he is awakened by his wife Ekwefi. Their daughter Ezinma, whom Okonkwo is fond of, is dying. Okonkwo gathers grasses, barks, and leaves to prepare medicine for Ezinma.
A public trial is held on the village commons. Nine clan leaders, including Okonkwo, represent the spirits of their ancestors. The nine clan leaders, or egwugwu, also represent the nine villages of Umuofia. Okonkwo does not sit among the other eight leaders, or elders, while they listen to a dispute between an estranged husband and wife. The wife, Mgbafo, had been severely beaten by her husband. Her brother took her back to their family's village, but her husband wanted her back home. The egwugwu tell the husband to take wine to his in-laws and beg his wife to come home. One elder wonders why such a trivial dispute would come before the egwugwu.
In her role as priestess, Chielo tells Ekwefi (Okonkwo's second wife) that Agbala (the Oracle of the Hills and Caves) needs to see Ezinma. Although Okonkwo and Ekwefi protest, Chielo takes a terrified Ezinma on her back and forbids anyone to follow. Chielo carries Ezinma to all nine villages and then enters the Oracle's cave. Ekwefi follows secretly, in spite of Chielo's admonitions, and waits at the entrance of the Oracle. Okonkwo surprises Ekwefi by arriving at the cave, and he also waits with her. The next morning, Chielo takes Ezinma to Ekwefi's hut and puts her to bed.
When Ogbuefi Ezeudu dies, Okonkwo worries because the last time that Ezeudu visited him was when he warned Okonkwo against participating in the killing of Ikemefuna. Ezeudu was an important leader in the village and achieved three titles of the clan's four, a rare accomplishment. During the large funeral, Okonkwo's gun goes off, and Ezeudu's sixteen-year-old son is killed accidentally.
Because the accidental killing of a clansman is a crime against the earth goddess, Okonkwo and his family must be exiled from Umuofia for seven years. The family moves to Okonkwo's mother's native village, Mbanta. After they depart Umuofia, a group of village men destroy Okonkwo's compound and kill his animals to cleanse the village of Okonkwo's sin. Obierika stores Okonkwo's yams in his barn and wonders about the old traditions of the Igbo culture.
Okonkwo is welcomed to Mbanta by his maternal uncle, Uchendu, a village elder. He gives Okonkwo a plot of land on which to farm and build a compound for his family. But Okonkwo is depressed, and he blames his chi (or personal spirit) for his failure to achieve lasting greatness.
During Okonkwo's second year in exile, he receives a visit from his best friend, Obierika, who recounts sad news about the village of Abame: After a white man rode into the village on a bicycle, the elders of Abame consulted their Oracle, which told them that the white man would destroy their clan and other clans. Consequently, the villagers killed the white man. But weeks later, a large group of men slaughtered the villagers in retribution. The village of Abame is now deserted.
Okonkwo and Uchendu agree that the villagers were foolish to kill a man whom they knew nothing about. Later, Obierika gives Okonkwo money that he received from selling Okonkwo's yams and seed-yams, and he promises to do so until Okonkwo returns to Umuofia.
Six missionaries, including one white man, arrive in Mbanta. The white man speaks to the people about Christianity. Okonkwo believes that the man speaks nonsense, but his son, Nwoye, is captivated and becomes a convert of Christianity.
The Christian missionaries build a church on land given to them by the village leaders. However, the land is a part of the Evil Forest, and according to tradition, the villagers believe that the missionaries will die because they built their church on cursed land. But when nothing happens to the missionaries, the people of Mbanta conclude that the missionaries possess extraordinary power and magic. The first recruits of the missionaries are efulefu, the weak and worthless men of the village. Other villagers, including a woman, soon convert to Christianity. The missionaries then go to Umuofia and start a school. Nwoye leaves his father's hut and moves to Umuofia so he can attend the school.
Okonkwo's exile is over, so his family arranges to return to Umuofia. Before leaving Mbanta, they prepare a huge feast for Okonkwo's mother's kinsmen in appreciation of their gratitude during Okonkwo's seven years of exile.
When Okonkwo returns to Umuofia, he discovers that the village has changed during his absence. Many men have renounced their titles and have converted to Christianity. The white men have built a prison; they have established a government court of law, where people are tried for breaking the white man's laws; and they also employ natives of Umuofia. Okonkwo wonders why the Umuofians have not incited violence to rid the village of the white man's church and oppressive government.
Some members of the Igbo clan like the changes in Umuofia. Mr. Brown, the white missionary, respects the Igbo traditions. He makes an effort to learn about the Igbo culture and becomes friendly with some of the clan leaders. He also encourages Igbo people of all ages to get an education. Mr. Brown tells Okonkwo that Nwoye, who has taken the name Isaac, is attending a teaching college. Nevertheless, Okonkwo is unhappy about the changes in Umuofia.
After Mr. Brown becomes ill and is forced to return to his homeland, Reverend James Smith becomes the new head of the Christian church. But Reverend Smith is nothing like Mr. Brown; he is intolerant of clan customs and is very strict.
Violence arises after Enoch, an overzealous convert to Christianity, unmasks an egwugwu. In retaliation, the egwugwu burn Enoch's compound and then destroy the Christian church because the missionaries have caused the Igbo people many problems.
When the District Commissioner returns to Umuofia, he learns about the destruction of the church and asks six leaders of the village, including Okonkwo, to meet with him. The men are jailed until they pay a fine of two hundred and fifty bags of cowries. The people of Umuofia collect the money and pay the fine, and the men are set free.
The next day at a meeting for clansmen, five court messengers who intend to stop the gathering approach the group. Suddenly, Okonkwo jumps forward and beheads the man in charge of the messengers with his machete. When none of the other clansmen attempt to stop the messengers who escape, Okonkwo realizes that they will never go to war and that Umuofia will surrender. Everything has fallen apart for Okonkwo; he commits suicide by hanging himself.