Cry, the Beloved Country is a tragedy, so it makes sense that the ending is, well, sad. At the same time, there is a ray of hope: this book won't leave you feeling miserable. After all, Paton does not want us to despair over South Africa's future. The novel both acknowledges that bad stuff has gone on and tries to suggest that things may get better.
Kumalo spends the last chapter sitting at the top of a mountain. He has apparently climbed this mountain twice before, in times of great emotional upset. And this evening definitely counts as emotional upset for Kumalo, since Absalom is going to be executed at dawn the next day in the capital city of Pretoria.
Kumalo climbs this mountain near Ndotsheni to, literally, get away from it all. He goes to find perspective and to meditate and to mourn his son's death. Since this book is much more concerned with Kumalo's emotional responses to his son's fate than with what actually happens to Absalom, we stay beside Kumalo as he waits through the night on his mountaintop. Paton doesn't bother to represent the execution, since we know that it is coming. Instead, he avoids the violence of such a scene, emphasizing Kumalo's honest prayer and thanksgiving for all that is good in his life. Kumalo certainly takes seriously the novel's Christian message to avoid despair and to have faith in God's larger plan for the universe.
As the novel winds down, it opens out from Kumalo's personal story to a larger narrative of South Africa itself. Kumalo watches the dawn coming and observes that the village in the valley is still dark: "The great valley of the Umzimkulu is still in darkness, but the light will come there. Ndotsheni is still in darkness, but the light will come there also" (3.36.56).
The repetition in this passage makes the writing sound like a prophecy or a prayer in its own right. Clearly, Paton is calling on the symbolism of light and dark to talk about good and evil in South Africa, and to pray for reform. The town of Ndotsheni is "still in darkness" because it suffers from the inequality and poverty that Kumalo and Jarvis are working hard to change. The hopeful statement that "light will come there also" implies that someday, Ndotsheni and the great valley of Umzimkulu—and all of South Africa—will eventually see the light, that they will someday become more integrated and less racially divided places.