The young Galingré is looking for his father's murderer, Hamd el Amasat, and falls into a trap. Although Kara Ben Nemsi becomes suspicious, he can no longer save him. Kara Ben Nemsi takes up the chase with his new servant, Halef. In the swamp they meet Sir David Lindsay and his secretary Nelly, who join them - just like their guide Omar Ben Sadek. In the Kbilli oasis they meet the villain again and are brought to justice by the bribed Wekil. When the tide begins to turn, the Onbaschi puts on a coup and puts down the Wekil. In the general turmoil, the killer escapes. They follow him to the "dead city", a ruined city with an underground rock labyrith, and are ambushed there. Fortunately, nothing happens to them. Amasat escapes seriously injured.