A researcher in infertility, Peter Cotton has developed a serum based on the rabbit sex drive to help couples conceive. Unbeknownst to him, the military has secretly funded the research to create a rabbit soldier that is vicious in battle and can breed in the field. After Peter realizes this, he attempts to stop the project with disastrous results. He is bitten by one of the military's mutant rabbits and a large dose of serum is dumped into the wound. Peter transforms into the evil Rottentail.