Mumbi, Kihika's sister is the pivotal character in the novel. Mumbi "was said to be one of the most beautiful women on all the eight ridges" and, owing to her looks, she was compared to Wangu Makeri, the last of the great Gikuyu queens. Mumbi is Kihika's sister, Gikonyo's wife, has a child by Karanja and is Mugo's closest confidant. Apart from the narrative line, which ends with Mugo's confession, trial by the village elders and supposed death, the second most important narrative line is the competition between Gikonyo and Karanja for Mumbi's love.
Gikonyo becomes Mumbi's husband, but while Gikonyo is in detention, Karanja, who is the local Chief by this time working under the jurisdiction of the British, helps Mumbi find a secondary school place for Mumbi's brother Kariuki.When Karanja tells Mumbi that Gikonyo is to be set free, Mumbi allows Karanja to make love to her. When Gikonyo arrives home from prison, he discovers that Mumbi is expecting Karanja's child. By the end of the novel, Karanja, who had betrayed his oath and many Mau Mau members from his village, goes off to a life in exile at Githima.
