In River Falls, in the night, Jack Flynn is driving home his old truck along a lonely road with the birthday gift for his daughter Carol, when he has a car crash. On the next morning, Carol meets her boyfriend and school mate Mike Simpson and asks him to borrow a car to look for her missing father. They find his truck off road and enter in a nearby cave to seek out Jack. They stumble upon with his body and then with a giant cobweb and a spider. They flee and look for Sheriff Cagle to report the incident but the old man believes it is a prank. However, their Professor Art Kingman believes them and forces the sheriff to organize a party to search Jack Flynn. They find that the teenagers are telling the truth and use a large concentration of DDT to kill the spider. Kingsman brings the arachnid to the town to send to the university, but the spider is not dead an brings havoc to River Falls.