Harry Goldman is back once more, and this time he's living the domestic life up in the Catskill Mountains with Anastasia, his transgenic girlfriend. At the end of Catnip 2: Rise of the Transgenics, he went through the same process as Anastasia did. Now he's the same as she is, and their only wish is to be left alone and to live their lives in peace.

Their peace is shattered by the arrival of a pig-man named Istvan. It seems that Istvan escaped from a laboratory in Hungary where yet another scientist was conducting transgenic experiments. In short order, the young couple is confronted by Szabo, a giant of a man who is more shark than man. He has plans not only for himself but also for others who wish to become as he is.

This is something that Harry cannot allow. Soon he, Anastasia and Istvan are circling the globe and making stops in Hungary and Serbia. Their journey ends in Russia where it all began. There, Harry meets the real brains behind the transgenics program and is once more involved with his girlfriend in a battle against those who'd destroy society, a battle that could very well cost them their lives.