Muddy Waters is a small river port in Darkwood, on the edge of a vast, largely unexplored swamp ominously named Green Shroud.
Here, Zagor and Chico join an expedition organized by Dorothy Sanders, a young woman determined to discover the fate of her brother Leonard, assistant to a brilliant scientist, Professor Howenstein. The group also includes two guides, Olson and Demas, Dr. Lambert (who has come to replace Leonard), and Slater, the professor’s right-hand man escorting a shipment of exotic animals.
The group arrives at New Genesis, the laboratory Professor Howenstein has set up in the Green Shroud swamp, and is greeted by Byron, the professor’s hunchbacked assistant, who shows them Leonard’s grave (which, however, turns out to be fake).
Meanwhile, a terrible and mysterious predator brutally kills one of the two guides, who is then “treated” by Howenstein and turned into a beast-like creature, similar to others that dwell in that place.
Indeed, the nature of the experiments conducted at New Genesis is deeply sinister, and Zagor soon uncovers the horrifying secret hidden in the swamp lab: Howenstein aims to return to humans the physical traits he claims were lost during evolution, by extracting substances from animal glands with the result that men are transformed into monstrous creatures.
Needless to say, he pays dearly for this offense against the laws of nature or perhaps even the divine!
