Tom’s brother, in his mad scientist phase, experiments by dunking Frankie, the family goldfish, into a vat of toxic green sludge. Through a desperate attempt to save his pet, Tom zaps Frankie with a battery—only to bring him back as a zombie goldfish with hypnotic powers and a bitter grudge. Frankie begins exacting revenge, and now Tom must try to stop him before the goldfish’s schemes spiral out of control.