A parasitic alien soul is injected into the body of Melanie Stryder. Instead of carrying out her race's mission of taking over the Earth, "Wanda" (as she comes to be called) forms a bond with her host and sets out to aid other free humans.

An inspired experimental chemist, wakes up in a New Orleans jail, accused of arson that's linked to an illegal drug-manufacturing ring. Suffering from amnesia, he's unexpectedly released on bail, determined to find his missing girlfriend.

On Halloween night, a sorority house is overrun with ghosts, while a vengeful housemother goes on a killing spree.