A secret military project accidentally unleashes genetically engineered, flesh-eating piranhas into a river system, leading them to a popular summer resort and camp, forcing investigator Maggie McKeown and guide Paul Grogan to race against time to stop the ravenous fish before they slaughter the vacationers. Created by a rogue scientist for the Vietnam War, these piranhas are smarter and tougher than normal, requiring extreme measures to contain them as they head for their next meal at Lost River Lake.