The drums sound out a message across the jungle. Tarzan has become an enemy stealing young women from their tribe. A young English woman who is the daughter of a millionaire has also been kidnapped. The millionaire has offered a huge reward for the capture of Tarzan and the return of his daughter.
Tarzan is not responsible but real pissed that an imposter is ruining his reputation. So he embarks on a quest to bring to justice the imposter. He tracks him to a lost city of descendants of Portuguese explorers.
The twenty-third book in the series is OK. It was interesting but nothing really memorable. This story was found in Burroughs years after his death. Maybe he had plans to improve on it. If you read the first twenty-two you might as well read this one.