Waiyaki, the protagonist of The River Between, would certainly appear to fulfill the basic requirements of a tragic hero, at least as the term normally applies to Greek tragedy. A fundamentally decent man, Waiyaki is ultimately brought low by a flaw that is itself tragic.
In many Greek tragedies, this flaw is hubris—that is to say, excessive pride or self-confidence. But in this African variant of ancient Greek tragedy, the relevant flaw is a lack of self-knowledge.
Despite his obvious intelligence, despite his extensive education, and despite his imbibing the white man's knowledge, Waiyaki doesn't really know himself. He thinks that he can somehow cut across the various complex power relationships that exist in this part of the world and build an alliance that will challenge colonial rule. As events will show, Waiyaki is fundamentally mistaken in believing this to be possible.
Among other things, Waiyaki's lack of self-knowledge means that he's unable to overcome the numerous obstacles placed in his way and that will prevent him from fulfilling the role of savior to his people. As well as representing a personal tragedy for Waiyaki, this is also a tragedy on a much larger scale for the people who live in this part of East Africa.