In a secluded lab, Dr. Kurt Leopold, a deranged former Nazi scientist, concocts a scheme to transform himself into a human-catfish hybrid using a serum he developed. Desperate for revenge on those who mocked his scientific ambitions, he injects himself with the formula, successfully altering his physiology. Now a monstrous creature, he sets out to exact his vengeance on the small Florida town, targeting those who doubted his work. As the creature wreaks havoc, mysterious disappearances and gruesome murders leave the community in fear and confusion, drawing the attention of local authorities and scientists.

A team led by marine biologist Rex and Sheriff Lou, along with federal agents, arrives to investigate the bizarre incidents. They uncover alarming clues that point to a mutated aquatic creature responsible for the carnage. Meanwhile, Leopold, now fully consumed by his monstrous form, continues to terrorize the town and kidnap innocent victims to perfect his twisted experiments. As the frequency of attacks increases, the investigators race against time to track down and stop the creature before it destroys everything in its path.