Nathan's lack of love for his family is also his betrayal of them. He rules them with an iron hand, cruelly abusing them. He betrays them when he doesn't allow his wife or daughters to explore any sense of themselves outside of the family. His wife, Orleanna, knows he could never love her because he believes it's his duty to save the Africans from themselves.
Orleanna loves her daughters, but she continues to stay with Nathan, thus betraying her daughters. It isn't until Ruth May, her youngest daughter, dies that she gets the courage to try and get her other daughters out of Africa. Ruth May's death haunts her for the rest of her life, and she feels she betrayed her by not taking her daughters out sooner.
The major theme of the book is the effect of colonialism on the people of Africa. The effect of colonialism is seen through the eyes of the Price family. Europe and the U.S. exploited Africa for its riches, forcing its people into labor. This colonialism is a betrayal of the people of Africa and the love those people have for their country. Colonialism destroyed their traditions, bringing chaos into their lives.