Petals of Blood relies heavily on flashbacks, using the points of view of the four major characters to piece together previous events. As each character is questioned by the police, the novel takes on certain characteristics of the detective novel, with a police offer trying to ascertain details of their pasts in order to find the murderer of Chui, Kimeria, and Mzigo. The flashbacks also encompass several different timeframes. The present day action takes place over the course of 10 days; the past events take places over 12 years. Ngugi also discusses Kenya's past, going as far back as 1896, when Kenya was "annexed" by the British.
The narrative voice shifts between Munira and the other characters describing the events of their lives, and an omniscient narrator. There is also a suggestion of a communal narrative voice, as Ngugi draws on the mythic past of Kenya to place the novel in a wider context than simply the colonial. This communal voice is at work through the various Gikuyu songs with which Ngugi intersperses the novel; there is a great reliance placed on such songs, which help tell, through the oral tradition of linking of proverbs and fables, the history of Ilmorog and Kenya before colonial intervention.