At Port-la-Nouvelle, on the parched terrain of central Africa, Dr. Mallory watches as his clinic fails and dreams of discovering a third Nile that will make the Sahara bloom. When there is a trickle on the local airstrip, and soon a river, the obsessed Mallory claims it as his own creation. Joined by Noon, a silent adolescent girl who as a child ran with the local guerrillas; Professor Sanger, a documentary filmmaker with a fading reputation; and...