On his departure from the Gallugos, Tarzan is given a Cape buffalo calf. He gives it the growth food and trains it. He decides to visit his friends in A-lur. When he arrives, he finds that King Taden's cousin, Kodon, is in rebellion. Tarzan and his buffalo help put down the rebels.; Two hunters are sold to slavers bound for Castra Sanguinarius, a city inhabited by the descendants of ancient Romans. Tarzan tracks the slavers and wins the hunters' freedom by promising to return and take their place in the gladiators' pit.; Boy and Dombie create home-made bombs to drive away marauding baboons.; Nagopa attempts yet another coup, but Tavane declares her right to rule Aba Zulu and she is supported by the people. A shipwreck frees Dan-El and Natongo from the slavers.