A spider escapes from an isolated desert laboratory experimenting in giantism and grows to tremendous size as it wreaks havoc on the local inhabitants. In the Arizona desert, Professor Gerald Deemer is experimenting with growth hormones in the hopes of finding a way to increase the world's food supply. His partner in the project was recently found dead in the desert, suffering from a disease that normally takes years to advance but in his case seems to have afflicted him in only a few days. The local doctor, Matt Hastings, is puzzled by the strange case and with Deemer's recently arrived - and very pretty - assistant Stephanie Clayton tries to figure out what is going on. When cattle remains are found in the countryside, the evidence points to a giant tarantula as the culprit.