In parched, war-torn 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 up-river in an old car ferry, clashing with hostile factions as he tries to find the source of his own creation.