It's the first comet to buzz our planet Earth in 65 million years, and everyone seems to be celebrating its imminent arrival. Everyone except Regina Belmont, and her younger sister Samantha, two Valley Girls who care more about fashion trends than celestial phenomena. But upon daybreak, when the girls discover that they are the only residents of Los Angeles whom the comet hasn't vaporized or turned into a zombie, they would do what all Valley Girls do - they go shopping. However, with the help of a friendly truck driver, the girls save Earth and escape from flesh-eating zombies and blood-seeking scientists in hot pursuit.