 The parachutist landing in the alligator pit, as well as the slaughterhouse footage, the shootout in front of the pharmacy and monkey brain eating sequence are lifted whole from the earlier films.In between there are brief introductory scenes featuring James B. Schwartz as "Dr. Louis Flellis".Flellis explains that his friend and mentor Dr Francis B. Gröss died while Flellis himself was performing a routine operation on him, although it remains unclear why.