An alien spacecraft crashes down in a U.S. national park. A mosquito sucks the blood of the craft's deceased Extraterrestrials in fiction pilot, causing the insect to mutate to an abnormally large size. While driving to a summer camp in the park, lovers Megan and Ray accidentally hit the mosquito. They get out of the vehicle, and Ray finds its severed proboscis in his car's radiator. Meanwhile, a park ranger named Hendricks is ordered by the park chief to spray gaseous mosquito repellent.