At the start of the film a meteor carrying a parasitic alien crashes into the woods near the rural town of Wheelsy. A couple who is fooling around nearby go to investigate and are attacked and infected.
Later we see the man, a car dealer named Carl, returning home. He is slowly transforming but he looks normal for now, although he behaves oddly, being possessed. His wife Starla starts to notice the changes and figures out that something is amiss. Scared, she turns to Sheriff Bill Pardy, who she is secretly in love with.
Meanwhile we find out that the woman Carl was fooling around with, Brenda, has been transformed monstrously and is hidden in an isolated barn. She is impregnated with a huge brood of parasites that are meant to spread out and take over the rest of the townsfolk.
Carl becomes increasingly grotesque and the Sheriff rounds up some volunteers to chase him down when he flees into the woods, but along the way they discover Brenda who is now huge and ready to release the parasites in the form of hundreds of slug-like creatures.
While they watch in horror she literally explodes and the slug infestation quickly takes over most of the town, turning the population into an alien hive mind. Aside from Starla and the Sheriff, only the mayor and one teenage girl are left uninfected, and together they try to survive and escape.
Best part of story, including ending:
The monster was pretty cool and scary.
Best scene in story:
I liked the scene where Grant is fully transformed and escaping into the field.
Opinion about the main character:
The Sheriff is very wry and his conflicted feelings about Starla quite sweet.