Stephen Conroy

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.

On Halloween night at a horror theme park, a costumed killer begins slaying innocent patrons who believe that it's all part of the festivities.