| Director | Frank Marshall, Frank Marshall |
|---|---|
| Budget | $22 million |
| Box office | $53.2 million |
In a remote Venezuelan tepui, British entomologist Dr. James Atherton leads an expedition to discover new insect species. His photographer, Jerry Manley, is bitten by a previously undiscovered, highly venomous spider of prehistoric origin, and suffers a severe seizure from the venom and dies. Atherton and his crew send Jerry's body back to his hometown of Canaima, California, unaware that the spider has crawled into the coffin.
Jerry's desiccated body arrives at the mortuary of mortician Irv Kendall. The spider escapes from the coffin, is picked up by a crow and bites the bird. The crow falls dead outside the barn of Ross Jennings, a family physician who has moved from San Francisco to take over the practice of the retiring town doctor. Ross and his son both suffer from arachnophobia.
Ross is short of patients after Sam Metcalf, the elderly town doctor, hesitates about retiring. The Venezuelan spider mates with a house spider in the Jennings' barn. The domestic spider produces hundreds of infertile, drone offspring with their father's lethal bite, and they leave the nest after consuming their mother.
Ross's first patient, Margaret Hollins, dies after being bitten by one of the new spiders, and he doubts Metcalf's diagnosis of a heart attack. Another arachnid kills high school football player Todd Miller just after Ross conducted a routine team checkup, earning him the nickname of "Dr. Death". The next victim is Metcalf himself, who is bitten and dies in front of his wife.
With Metcalf dead, Ross becomes Canaima's town doctor. Knowing that Metcalf was bitten by a spider and a "minute amount of an as-yet unidentified toxic substance" was detected in his body, he suspects that the town may be infested by deadly arachnids.
Ross calls Atherton and asks him to help his investigation. The skeptical entomologist sends Chris Collins, his assistant. Ross and county coroner Milt Briggs order that Margaret and Todd be exhumed. They perform autopsies, and Chris confirms Ross's suspicion after he identifies bite marks. Ross and Chris catch two of the spiders (one had died of a natural cause) in Metcalf's house the following day. When Chris mentions the new species discovered by Atherton, Ross realizes that the town's killer spiders and Atherton's discovery are related.
Atherton joins Ross, Chris, Milt, Sheriff Lloyd Parsons, and exterminator Delbert McClintock in Canaima, and they discover the spiders have a short lifespan due to their crossbreeding. Atherton tells them that the spiders are soldiers sent to eliminate potential threats for the male spider leading the colony, which he calls "the general". He learns that the general produced a queen and inbred with her to produce a second nest (guarded by the queen) which could produce fertile offspring, culminating in the species' next stage of evolution and worldwide dispersal.
Ross, Chris, and Delbert discover that one nest is in Ross's barn. When he destroys the nest, Delbert finds Atherton dead. He had attempted to catch the general and purposely touched a strand of the web to coax the spider out, but was bitten by the male spider which then escaped. Chris gets the Jennings family out of their infested house, but Ross falls through the floor into his wine cellar: the spiders' second nest, guarded by both the queen and the general.
After he electrocutes the queen, Ross battles the general while he tries to burn the second egg sac (overcoming his fear of spiders by focusing on his need to stop them). Trapped by fallen debris as the general prepares to bite him, Ross stays perfectly still until the general is in position, then flings the spider into the fire. Despite being badly burnt, the general leaps out from the fire just as the egg sac hatches. Ross shoots the general with a nail gun, sending the flaming spider into the egg sac and destroying the nest. Delbert rescues Ross; with the general, the queen and the nests destroyed and the soldiers dying, the spiders' threat is over. Deciding that they missed their old life, the Jennings family returns to San Francisco. As they celebrate their safe return home, an earthquake hits, which they prefer over deadly spiders.