Reba, the poacher who managed to survive the battles with the crocodiles in the store in the third film, is now an EPA agent who attempts to exterminate the crocodiles in Black Lake. The lake has been corralled by the Army Corps of Engineers with a 10,000-volt electric barrier to lock the crocodiles in the lake to let them starve and die off. Reba and her group are scheduled to get inside the lake to capture young crocodiles for examination. However, they soon discover that the crocodiles have survived by cannibalism, which makes them continue breeding and increase their strength and aggressiveness. The problems become more serious when a group of students of Marshfield Swimming Team and an illegal group of hunters led by Jim Bickerman, who want to find crocodiles eggs, decide to trespass. Afterward, they all have to continue fighting the giant killer crocodiles until the group can escape the barrier.