Wealthy industrialist Robert Talbot arrives early for his annual vacation at his luxurious Italian villa to find three problems lying in wait for him. Firstly, his long-time girlfriend Lisa Fellini has given up waiting for him to pop the question and has decided to marry another man. Secondly, the major domo of his villa, Maurice Clavell, has turned the estate into a posh hotel to make some easy money while the boss isn't around. And, finally, the current guests of the "hotel" are a group of young American girls trying to fend off a gang of oversexed boys, led by Tony, who are 'laying siege' at the outer walls of the villa. Talbot, to his own surprise, finds himself becoming an overprotective chaperone.

While on a fishing trip, Harry Baldwin (Ray Milland) and his family hear an explosion and realize that Los Angeles has been leveled by a nuclear attack. Looters and killers are everywhere. Escaping to the hills with his family, he sets about the business of surviving in a world where, he knows, the old ideals of humanity will be first casualties. Not one to give up, he holds up a store for supplies and hides the family in a cave.

Thought to be killed by the sole survivor of the last massacre at Camp Crystal Lake, Jason Voorhees kills his way back to the camp to once again murder its inhabitants. This time, has Jason met his match in the little boy Tommy Jarvis?