This reprints the serialized story that was originally published in Dark Horse Presents 8-10. It begins with Tarzan picking up some supplies at a store and walking outside into a jungle that used to be London. We immediately find out that's he's a wanted man by The Tower Society and that he lives in a building where the only access is through a pool inhabited by crocodiles. This is where he keeps his protected collection of animals-those who haven't quite adapted to earth's new environment. However, there are some intruders and he's attacked by some ape-like humans. It turns out that they want his help against some military guys. Along the way on their quest through a flooded London they encounter some mutant killer plants, what looks like a mammoth and these weird, creepy crab-people. He eventually reveals to them that he's really Tarzan of the Apes and that he hasn't aged because of that magic potion taken a few hundred years before in Africa. And in the end he's reunited with his wife, Jane, who also hasn't aged.
This is a great follow-up to TARZAN: THE BECKONING, and is a good continuation of the Tarzan mythos.