In parched Port-la-Nouvelle in Central Africa, Dr Mallory watches his clinic fail and dreams of discovering a third Nile to make the Sahara bloom. During his search for water, an ancient tree stump is uprooted by a bulldozer and water wells up, spreading until it becomes an enormous river. With the once arid land now abounding in birds and beasts, the obsessed Mallory forges upriver, clashing with hostile factions in his quest to find the source of his own creation.