At a wild teenage party in a small apartment, the kids suddenly turn against everything around them and trash the apartment to complete annihilation. They kids are called Destruction Inc.; a bunch of self-imposed derelicts that terrorize a sleepy Florida town. They are led by the near-psychotic Dexter (Ray Sager), his pal Denny (Steve White), Denny's girlfriend Bitsy (Nancy Lee Noble), and their friend Lummon (Ralph Mullin). Their reason for forming this so-called "destruction crew" is as Dexter states: "just for the hell of it."
Dexter, Denny, Bitsy, and Lummonx stop at a local neighborhood bar for a few drinks when the bartender becomes irrigated with their shenanigans and orders them to be quiet in which they respond by beating up the owner and trashing the whole bar. Afterwards, Dexter and a few of the Destruction crew pile into Dexter's 1967 white Mustang car and drive around town terrorizing and harassing the locals. One teenybopper steals a lady's newspaper and sets fire to it. A man is splashed painted when a few other youths throw paint at him. Also, a police officer is contemptuously taunted.
At a corner coffee shop, the overly zealous teens engage in a bloody fist fight with another teenager, named Doug (Rodney Bedelle) whom used to know Dexter and was part of his gang before walking way years ago. As result of the rumble, the group begins to trash the place. The proprietor threatens to call the police, but is cut short when one of the teenyboppers punches him in the face. Dexter and Denny, aided by other Destruction crew, cruelly drag the owner to the stove and they unmercifully burn his hands on the hot stove.
Soon, newspapers decry the terrible savagery besieging the town, and the police proceed to track down and arrest Dexter and a few of his thugs. But under interrogation, the psychopath Dexter calmly denies anything to do with the violence sweeping the community. With no witnesses willing to come forward on fear of retribution from the Destruction crew, and with circumstantial evidence to hold him on, the police release Dexter, only giving him a warning to keep out of trouble.
Soon, the delinquents run afoul of law and order again. A blind man is ruthlessly tormented, and a newly bandaged man is beaten with his own crutches. The mindless debauchery continues as a throng of the cretins snatch a woman's baby and stash it in a garbage can, before they demolish the baby stroller, all in front of the mortified mother. Employees of a business office are harassed to a point of terrorism, and a local cafeteria is raided. An off-duty police officer is beaten, while a female homemaker is attacked while innocently laundering clothes. Desiring to slight no segment of society, a group of the Destruction crew invade a little league baseball game. A brawling free-for-all is interrupted by the good Samaritan, Doug, who witnesses the antics and intervenes, beating up a few of the crew, before he gets overwhelmed. A confused and senile old woman sees the rumble and calls the police, but the gang flees, and Doug unbelievably gets arrested for fighting with the boys. Go figure!
While Doug is temporally in jail, four of the gang cruise a road near the beach and discover a teenage couple making out on a beach blanket. The four teenyboppers attack and beat up the boy, while the young woman is gang raped and afterwards, both her and her boyfriend are bludgeoned to death by the sadistic youths who withdraw from the scene of the crime. Later, during a party the Destruction crew throws at their hideout, Dexter catches four high school girls who stumble into the party, and the group proceeds to strip and humiliate the naive and defenesless teen girls before throwing them out.
The next day, Doug is bailed out of jail by his girlfriend, Jeanne (Agi Gyenes) whom they both try to stop the gang on their own since the police are unwilling to do anything. Dexter and his group meet with Doug where they tell him to stay out of their way, but Doug refuses to be bullied. Apparently Dexter and Doug knew of each other when they were younger in which Dexter gave up everything for the quick and easy life of crime and vandalism. With Doug unwilling to back down, Dexter decides to get back at his former friend.
One evening, Bitsy phones Doug and lures him away from his house to meet with him on the ruse that she wants to help turn the gang she it in whom treat her like their mascot, Doug goes... leaving Jeanne alone in the house. Dexter, Denny and the Destruction crew arrive at the house shortly thereafter where they taunt, strip and severely beat and mutilate Jeanne before leaving her for dead. When Doug realizes that Bitsy has no intention of testifying against Dexter and the Destruction crew, Doug flees back to his house only to find Jeanne hideously bruised, bleeding, and maimed... with the image of a rat carved into her stomach.
Fuelled by revenge, Doug sets out back to the Destruction crew's hideout to confront them. Most of the group flees in Dexter's Mustang while Denny and Bitsy escape on a motorcycle. Doug gives chase with them racing through the streets of the town. Soon, the police intervene in the chase, which ends when Denny and Bitsy accidentally slide off the road at a curve and hit a telephone pole which the motorcycle explodes. Denny and Bitsy are thrown off the motorbike, and are both killed by the impact.
The final shot shows that Dexter has somehow escaped from the police and meeting with Lummox who gives him an update on Denny and Bitsy's deaths as well as several of the gang members now in jail. Indifferent, Dexter replies with "who cares, man?"
The film closes with the caption: 'THE END... of the movie, but not the violence.'