Niels and Merkus return to the Jungle to mine diamonds. Tarzan agrees to this as long as they stay away from the gorillas. Niels and Merkus are threatened by Tublat, who they capture and plan to make money out of him. Tarzan sets out to free Tublat, despite Terk's protests and the past conflict between them. He finds their camp desert, but Renard Dumont explains that Niels and Merkus are already on the train with a gorilla. Tarzan reaches the train and frees Tublat, who then attacks him. After he leaves, Niels and Merkus are left to be killed by Tublat, but Tarzan decides that letting them kidnap Tublat is no better than letting him kill Niels and Merkus, so sets off to rescue them again, against Terk's advice. At the end of the episode, Niels and Merkus are angry because they are leaving with nothing, whilst Tarzan is proud that he did the right thing.
- This episode features Niels and Merkus, although the "Tarzan and the Volcanic Diamond Mine" episode, in which they were introduced in, wasn't released until the following July (because the episodes were aired out of order).