While camping in the woods, Polly Watt and her clumsy boyfriend Seth Belzer damage their tent. They decide to spend the night in a low-budget motel. Meanwhile the criminals, Lacey Belisle and Dennis Farell, have trouble with their runaway car while heading to Platt and they walk on the lonely road. When Polly passes by Lacey, she stops the car and the couple is rendered by Dennis. However, Polly hits something in the road and while replacing the tire, they are attacked by a weird splinter. The car overheats and they stop in a gas station, where they are trapped by zombies, victims of the splinter parasite.

Jason, is bit by a strange organism while on vacation with his girlfriend, Sam, at her sister's secluded farmhouse. The bite begins a transformation in Jason, and now the couple must race against time to figure out what happened to Sam's sister and her family, and what lies in store for them. All of these elements are tantamount to the ultimate fear addressed in the film, the fear of losing a loved one and worse, becoming a monster in their eyes.

An ancient pestilence called The Scourge has been set free in a small town after being entombed in a church's masonry for a century and a half. As bodies rapidly pile up, nothing stands between the spawning Scourge and the rest of the town except our young heroes Scott and Jessie who rediscover their love for each other in the process.

Strange things are happening in Riverdale, Illinois. A huge, seemingly alien structure has been found jutting out of the earth. Sent to investigate the origin of the mysterious object, Senator Walter Powers discovers that parasites from the center of the earth have infiltrated the town, taking control of the authorities and workers, making communication with the outside world impossible, and leaving the responsibility of stopping the invasion up to Powers and a small group of free individuals.

A scientist living in an apartment complex kills a girl and uses acid to destroy her internal organs, and then kills himself. While investigating, a doctor discovers that the scientist was doing experiments on the use of genetically engineered parasites as organ transplants. Soon, other people in the complex begin showing signs of carrying the parasites, spreading the things through wanton orgiastic abandon, and the complex begins suffering an attrition problem.

In 1959, an alien experiment crashes to earth and infects a fraternity member. They freeze the body, but in the modern day, two geeks pledging a fraternity accidentally thaw the corpse, which proceeds to infect the campus with parasites that transform their hosts into killer zombies.