Tromaville High School just happens to be next to a nuclear power plant; so when an accident happens (which is covered up by plant owner Mr Paley – played by Pat Ryan Jr.) radioactive water leaks into the school drinking fountain and disturbingly kills a Tromaville student.
The bad gang of the school, “The Cretins” are revealed to be once part of the Tromaville High honor society but have slowly been polluted by the nuclear power plant and are now violent, crazy thugs. The Cretins pick leaves from a radioactive marijuana plant located in the yard of the nuclear plant and sell it to Eddie (James Nugent Vernon) for $10.
Eddie is hosting an indoor bikini beach party that night and peer pressures his friend Warren (Gil Brenton) and Warren’s girlfriend Chrissy (Janelle Brady) into smoking the radioactive joint. The joint ,is destroyed by some dancers before they can smoke it. Later the drug shows itself to have potent aphrodisiac effects, leading to Warren and Chrissy having sex in Eddie’s loft.
However, that same night, both Warren and Chrissy have disturbing nightmares about hideously mutating, though these effects are seemingly gone by morning. Some time later, Chrissy discovers that she is pregnant, and spits a little monster into a nearby toilet. The creature travels through the water pipes and lands in a barrel filled with radioactive waste, and mutates into a bigger creature.
Meanwhile, Warren, tired of The Cretins constant bullying, ends up going on a radiation-fueled rampage, killing two of them, with no memory of the event once he comes to his senses.
Expelled from the school, and more importantly cut off from their customer base, The Cretins decide to assault the principal and forces him to use the schools Radiation Alarm to cause an evacuation, letting The Cretins bar the building and occupy it. They capture Chrissy as bait for Warren.
The Cretins hold Chrissy hostage in the basement and plan to kill her in front of Warren, but they are interrupted by the now adult monster…