One morning, the Ilmorog police detain the teacher Munira for questioning about the murder-by-arson of businessmen Chui, Mzigo, and Kimeria. They also arrest the crippled Abdulla and the political organizer Karega.
In a flashback to 12 years prior, Munira arrives in Ilmorog as the town’s new teacher. He starts drinking at Abdulla’s bar and suggests Abdulla send his young helper Joseph to school; Abdulla ignores him. Then Wanja arrives to visit her grandmother Nyakinyua. One night at Abdulla’s, Munira tells Abdulla and Wanja how he and his classmate Chui were expelled from the high school Siriana for organizing a strike against their racist headmaster Fraudsham. Touched, Wanja offers to work at Abdulla’s in Joseph’s place so Joseph can attend school. Another night, Wanja explains that she dropped out of middle school after a married adult man impregnated her.
One day, Munira finds Karega outside his home. Karega introduces himself as the son of Mariamu, who worked on Munira’s father Ezekieli’s farm. Karega went to Siriana after Munira but was expelled for another strike. He asks whether Munira heard Fraudsham left Siriana and Chui came back; Munira admits he didn’t. Later that night, Wanja is thinking how Ilmorog’s diviner Mwathi wa Mugo told her to have sex on the new moon to get pregnant. When Munira shows up at Wanja’s with Karega, Wanja asks Munira to walk with her. On their stroll, Munira asks Wanja what happened to her baby, and Wanja bursts into tears. Then Munira walks Wanja back to her hut, and she invites Munira inside for sex. They initiate an affair until one night at Abdulla’s, Wanja starts complaining about how little she earns and how awful Ilmorog is. The next day, she’s gone.
A year later, Munira asks his boss, Mzigo, to help recruit more teachers. Mzigo refuses but gives Munira an invitation to tea with Ilmorog’s MP, Nderi wa Riera. Munira goes to “tea”—only to discover that everyone who attends is forced to swear an anti-communist loyalty oath. Afterward, Munira goes drinking in Limuru—and runs into Wanja. She tells him that she’s been working at another bar. Her coworkers were forced to attend “tea.” When she avoided it, someone set her apartment on fire. She has decided to move back to Ilmorog. Munira and Wanja run into Karega, who tells them how he became a beggar after his expulsion. Wanja tells Karega to come to Ilmorog with them.
Munira hires Karega as a teacher. Meanwhile, Ilmorog is suffering a drought. After several months, Karega suggests they organize a delegation to ask Nderi wa Riera for aid in the city. As the delegation travels toward the city, Wanja tells Karega and Munira that after leaving Ilmorog, she began doing sex work. One night, she met a German man who lured her back to his house and almost raped her. After she escaped, a Kenyan lawyer picked her up in his car and gave her his card in case she needed help later.
On the journey, Joseph falls ill. The delegation decides to ask for shelter while they tend to him, but nobody will offer them shelter. When Wanja, Karega, and a farmer named Njuguna approach yet another house, guards catch them and lock them in a room. The homeowner, Kimeria, says he won’t free them until Wanja has sex with him. When Kimeria’s employee claims Wanja is Kimeria’s runaway wife, Njuguna argues Wanja should have sex with Kimeria to save Joseph. Humiliated, Wanja has sex with the man.
When the delegation reaches the city, Nderi wa Riera is on a business trip and won’t come back till the next day. Since they have nowhere to stay, Wanja suggests they ask the lawyer who saved her for shelter. At the lawyer’s house, Munira asks Karega about his experience at Siriana. Karega explains that he participated in a strike for a more Africa-centric curriculum under Fraudsham. After Fraudsham left, Chui replaced him. When the students went on strike again, Chui had Karega expelled.
The next day, Wanja, Abdulla, Munira, Karega, and Njuguna meet Nderi wa Riera in his office. Nderi wa Riera goes outside to talk to the full delegation, waiting in nearby gardens, and suggests they embark on another delegation to Gatundu. The delegation, outraged, throws things. Riera flees, returns with policemen, and insists they arrest Abdulla, Munira, and Karega. The lawyer successfully defends the men at trial, and newspaper coverage of the event publicizes Ilmorog’s difficulties. Various organizations pledge to help the town.
A little later, it rains in Ilmorog. The town plans a post-harvest celebration and circumcision ceremony. The afternoon of the ceremony, Wanja, Abdulla, Munira, and Karega gather with Nyakinyua and other elders to drink Theng’eta, a traditional drink with spiritual properties. When Karega drinks, he speaks about Munira’s sister Mukami. He and Mukami were in love, but Ezekieli—who believed Karega’s brother Nding’uri had cut off his ear during Kenya’s fight for independence because Ezekieli opposed the freedom fighters—demanded Mukami choose between her family and Karega, after which Mukami died by suicide. Abdulla, shocked, reveals he knew Nding’uri during the revolution; they were freedom fighters. One day, Nding’uri’s girlfriend’s brother sold them a gun. At the sale, the police arrived—the brother had tipped them off. Nding’uri was executed, but Abdulla escaped and swore revenge.
When the gathering disperses, Munira approaches Wanja and complains that they haven’t resumed their affair. Wanja dismisses him. She ends up walking with Karega and telling him that Kimera, the man who forced sex on her during the delegation’s journey, also impregnated her when she was an adolescent. She and Karega hold hands, and then he removes her clothes. She resists at first, but then they have sex. Afterward, Karega goes home and sleeps. Much later, Munira wakes him and says he was mumbling Mukami and Wanja’s names. He accuses Karega of causing Mukami’s suicide and claims they can’t work together. Karega, outraged, refuses to quit the school.
The next year, Munira hires three new teachers. One day, seeing Wanja and Karega make romantic eye contact, Munira travels to the headquarters. Later, Karega is fired. Wanja accuses Munira of getting Karega fired and says she’ll take revenge. Afterward, at Abdulla’s, she finds Karega and Abdulla talking. Abdulla is explaining that he fought to end economic exploitation—but after Kenyan independence, exploitation continued. When he discovered that the man who betrayed Nding’uri, Kimeria, had gotten rich after independence, it broke Abdulla’s spirit. Wanja starts sobbing. She explains Kimeria is the man who impregnated her as an adolescent. Then Wanja, Abdulla, and Karega hear a plane crash in a nearby field. Over the next few weeks, many people travel to Ilmorog to look at the plane. Wanja and Abdulla sell the tourists food and Theng’eta. Soon Theng’eta becomes a famous drink. Karega, meanwhile, leaves town.
Wanja and Abdulla start a Theng’eta brewery. One day, Nderi wa Riera visits Ilmorog and announces a plan to help local farmers develop their land with the help of bank loans. Many farmers cannot repay the loans, however, and their farms are repossessed. Wanja’s grandmother Nyakinyua is one of the farmers whose land is repossessed. Desperate, Wanja and Abdulla sell their business to Mzigo. Wanja uses her profits to save Nyakinyua’s land; she also builds a huge wooden bungalow. One night, she invites Munira there. Munira is excited—but when he arrives at the bungalow, Wanja announces her intention to start a brothel and demands Munira pay for sex. Meanwhile, Mzigo, Chui, and Kimeria all become directors of the company Theng’eta Breweries.
Five years after Karega left Ilmorog, he returns and visits Munira. Out of spite, Munira offers to take him to see Wanja without letting him know Wanja is a prostitute again. When Munira and Karega arrive at Wanja’s brothel, Karega and Wanja are shocked to see each other. As Wanja questions him, Karega explains that after he left Ilmorog, he worked for the lawyer who was running for office as a progressive reformer. Then Karega worked for docks, plantations, and a UK-owned sugar mill. Everywhere he went, Kenyan workers were exploited. Finally, Karega decided to come back to Ilmorog.
Wanja abruptly confesses that she tossed the baby she had as an adolescent into a latrine. Finding no goodness in the world after Karega left Ilmorog, she has decided to take revenge on Kimeria, Chui, and Mzigo by taking their money for sex and making them jealous of one another. Karega says that if the world is awful, people should make “a new world.” Karega’s words resonate with Munira. Disgusted by the world’s evil, Munira seeks consolation in religion but finds none in the established church. Then he hears that the lawyer has been assassinated. Horrified, Munira goes walking—and comes upon evangelical Christians preaching redemption by grace alone. He suddenly converts.
Meanwhile, Karega starts working for Theng’eta Breweries and writing pro-unionization political pamphlets. The workers unionize; the brewery fires Karega, but the union hires him. A week before the fire, Wanja warns Karega that Chui, Mzigo, and Kimeria plan to assassinate him. Karega thanks her for the warning but accuses her of siding with the exploitative capitalists and leaves. The same day, Abdulla gets a letter from Joseph, who has gone to Siriana and is doing extremely well. He goes to tell Wanja and runs into Karega leaving her hut. Abdulla finds Wanja and initiates sex with her. Later, she invites him to visit her at the brothel the following Saturday. She is secretly planning to gather Mzigo, Chui, Kimeria, and Abdulla, humiliate the first three by claiming Abdulla is her true romantic partner, and tell them all Kimeria’s wrongdoings.
The next Saturday, Mzigo, Chui, and Kimeria visit Ilmorog. Seeing Kimeria’s car, Abdulla abruptly decides to kill the man. He stakes out the brothel, not knowing that Wanja has already impulsively stabbed Kimeria to death. Then Abdulla sees the brothel is on fire. He breaks inside and rescues Wanja.
After Munira, Abdulla, and Karega are arrested, a police officer, Inspector Godfrey, interrogates them. Godfrey eventually realizes that Munira set the fire to kill Wanja. In a flashback, the now zealously religious Munira sees Karega enter Wanja’s hut and hears a voice telling him he has to rescue Karega from Wanja’s sexual wiles.
After Munira is charged with the murder, Wanja discovers she is pregnant, Abdulla feels grateful that the future of Kenya rests with young men like Joseph, and Karega recommits to the struggle for workers’ rights and economic equality.
