The film takes place aboard an American submarine in the Pacific during World War II. The sub's commander is ordered to stop and pick up an underwater demolition team led by Lt. Hayes, whose mission is to locate and destroy a US submarine sunken in a lagoon off Bikini Atoll before the Japanese are able to raise it and capture the advanced radar system on board.

A group of drag-racing fanatics, members of a Los Angeles club, move into an old deserted mansion and set up shop, making it their headquarters. They hold a Halloween masked ball for the club's grand opening, and invite everyone to come dressed as their favorite monster! Oddly enough, the festivities turn sour when one of the bright youths discovers an impostor among them in the form of an honest-to-gosh live monster who's been hogging all the dances with the best-looking girls