Petals of Blood is a novel of social and political criticism cast in the form of a crime story. Three directors of the local brewery in Ilmorog have died as a result of a fire. Arson is suspected, and the novel opens with the arrest of the four principal characters: Munira, the protagonist, headmaster of the school in Ilmorog; Karega, a teacher at the school; Abdulla, the owner of a local shop and bar; and Wanja, a young woman who works in Abdulla’s shop and who later becomes a prostitute.

The story then unfolds through a series of time shifts, moving from the present to the past. It was twelve years before the time of the fatal fire that Munira first made his way to the village of Ilmorog. He had come because he wanted to establish a school that would provide the village children with a good Christian education. At that time, Ilmorog was a dusty, sleepy, wasteland of a village, and since others had come before him and left, everyone in Ilmorog believed that Munira too “would go away with the wind.” Munira, however, is made of sterner stuff. He stays and enlists the support of others, including Abdulla, Karega, and the very attractive Wanja; a considerable part of the novel is devoted to revealing the manner in which the lives of these four people become entangled.

Inspector Godfrey, a strong believer in the police force as “the maker of modern Kenya,” is in charge of investigating the death of the three directors. Godfrey is a relentless interrogator of Munira and his friends, and through his investigation the reader learns about the four principal characters and their involvement with one another.

Ngugi also reveals the physical and spiritual changes that have transformed the village of Ilmorog from a “small cluster of mud huts” to a bustling new town “of stone, iron, concrete and glass and neon lights.” This transformation has brought with it much of the materialistic baggage associated with Western progress, and with this “progress” has also come corruption and the abuse of power. A multinational corporation owns the brewery, while the villagers are still poor; the wealth from the new Ilmorog is enjoyed by greedy investors from faraway Nairobi. Small shopkeepers such as Abdulla have been wiped out, and the beautiful Wanja has become a brothel owner to service the decadent desires of the new rich. The venerable hero of the Mau-Mau resistance is a ruined cripple in the free Kenya for which he had fought so hard, while the fat directors of the brewery enjoy a life of pleasure in exclusive country clubs.

The interrogation and the responses by the four principal characters are not presented in straightforward fashion; rather, information is provided in fragments and the reader is expected to follow the clues carefully. From the present, Ngugi moves to the past of the principal characters, and even to the past of their ancestors.

The four characters move back and forth from Ilmorog. When Munira first comes to Ilmorog, Abdulla is already there as a shopkeeper and bar owner. Wanja joins them, but her desire to marry Munira is doomed from the beginning, because Munira is still recovering from the trauma of his own failed marriage. Then comes Karega; there is a bond between him and Munira, because both of them were expelled from the high school which they attended in the village of Siriana. Ngugi uses this opportunity to describe the high school experiences which they shared; these reminiscences also sketch their schoolmate Chui, another important character, one of the three directors killed in the fire. In their youth, Chui was very much a rebel, but as the story proceeds the reader learns how Chui became a member of the establishment.

From time to time the four characters break off to go out on their own; Wanja and Karega return to their home region in the highlands, while Munira goes off to help the oppressed Kikuyu tribe. All four gather again, and involve themselves in traditional ceremonies and dances—a time of great joy in which they feel a strong identification with the roots of their culture.

Munira, a deeply religious man, is both puzzled and angered by Wanja’s illicit affairs; he is particularly disturbed by her secret meetings with Karega. As long as she lives, Munira believes, “Karega will never escape from her embrace of evil.” Feeling compelled to save Karega, almost looking upon it as a messianic duty, Munira sets fire to Wanja’s home, which to him is a “whorehouse.” As the fire consumes the house, the flames “forming petals of blood,” Munira is convinced that he is one with God and that he has obeyed the higher Law although he has broken man’s law. Having learned the facts of the case, if not their deeper meaning, Godfrey charges Munira “with burning Wanja’s house and causing the deaths of three men.”