During the Mahdist insurrection in the Anglo-Egyptian Sudan, veteran colonial Private Baker teams up with freshly arrived gentleman Murchison, trying to evacuate from southern Barash the Emir's daughter Asua and her English governess, Miss Woodville. It's a perilous journey on the Nile and its banks. They must face crocodiles, Arab slavers, and a backward Negro tribe they prey on, where King Gondoko's missionary-raised brother Kimrasi saves and joins them. Once in capital Khartum, they find the revolt has reached it and the men join the fight.