A mutant African cockroach infests a remote Maine island just as young Dr. Ben Cahill (Thomas Calabro) goes there to shake off the effects of his heavy drinking. His first encounter is with Jack Wolk (John Savage), a local who resents Cahill buying his family's dilapidated house. The resentment turns violent and Sheriff Hobbs (Dean Stockwell) is called in to cool things off. When his house turns out to have problems he can't fix, Cahill meets handywoman Nell (Kristen Dalton), who helps him out. But meanwhile, beneath the surface, those cockroaches begin reaching critical mass, attacking first animals and then humans as their numbers increase. The bugs use carcasses in which to breed, and soon they not only cover the ground, they also begin to fly.