In a series of experiences between 1856 and 1877, several British-born explorers tried to unravel the mystery of the source of the Nile. This river, the longest in the world, flowed through the desert, bringing life in its floodwater every year. Where did all this water come from? Christopher Ondaatje, long fascinated with Richard Burton and wishing to relive his 1856 African exploration, prepared for this journey by studying the expeditions of several Victorian travellers, for each had returned with part of the answer to the Nile's riddle. In 1996 Ondaatje followed the Victorian explorers' routes, to see for himself what they had seen. Although acutely aware that their claims of "discovering" a mountain or river were ridiculous, he quickly realized that he was indeed on a journey of discovery, and that the search for truth is often about finding new and better questions, not just answers. His trek across the Serengeti Plains to Olduvai Gorge provides the most striking revelation of all: the forces which shaped the Nile may also have triggered the evolution of the human race.