Ross Jennings: Jeff Daniels
Molly Jennings: Harley Jane Kozak
Delbert McClintock: John Goodman
Dr. James Atherton: Julian Sands
Sheriff Lloyd Parsons: Stuart Pankin
Chris Collins: Brian McNamara
Jerry Manley: Mark L. Taylor
Dr. Sam Metcalf: Henry Jones
Henry Beechwood: Peter Jason
Milton Briggs: James Handy
Irv Kendall: Roy Brocksmith
Blaire Kendall: Kathy Kinney
Margaret Hollins: Mary Carver
Tommy Jennings: Garette Ratliff Henson
Shelley Jennings: Marlene Katz
Directed: Frank Marshall
Screenplay: Don Jakoby and Al Williams
Story: Don Jakoby
Summary: Dr. Ross Jennings is troubled by peculiar deaths such as that of Margaret Hollins, a teacher, and of Dr. Sam Metcalf, who after working on a treadmaster is bitten by a spider hiding in his slipper and has a fatal seizure. County Medical Examiner Milt Briggs considers Ross a "hot shot who won't accept anyone else's diagnosis." But spider bite fatalities are rare and always have involved black widows.
Poison is determined to have been involved in the doctor's death, so spiders can't be ruled out and two previous deaths need reinvestigating by exhuming the bodies, despite the protests of Sheriff Lloyd Parsons. As Ross is investigating, his daughter has a sleep-over with a friend where they tell horror stories and sing "Itsy Bitsy Spider" and "Little Miss Muffit." We see a spider hovering around.
Ross studies arachnids at night and freaks at a cricket. He calls west coast authority Dr. James Atherton, who suspects scapegoating against spiders here until he hears the name of the town (since perhaps a Venezuelan spider hitched a ride in Jerry Manley's coffin).
His research assistant Chris comes instead and feels queasy at the examination of the exhumed corpses, where spider bites indeed are found. Atherton had better come. Ross, Chris, the Sheriff, and the Examiner enter a house. Chris finds webs outside, but the Sheriff finds a dead spider in a box of cereal from which he is eating.
Meanwhile, Henry Beechwood's daughter hogs the bathroom while a spider crawls into the other bathroom's toilet. The daughter takes a shower and a spider looms and jumps on her, getting washed down the drain. There's lots of screaming.
Back at the house, Chris and Ross find a spider alive in the dining room and capture it. "They're like little vampires."
Exterminator Dilbert is called in by Henry, whose bronco was also killed. He sprays individual spiders down the cracks on the deck.
The captured spider is shown to be able to kill a mouse. Since it has no sex organs, it must be a soldier, or drone, and we decide that a South American spider mated with a common domestic one. Since it will emerge at the top of the food chain and spread from a central locale, we're in trouble. In Venezuela geography contains them but here there'll be no stopping them. We need to find the primary nest.
A fat couple, Irv and Blaire Kendall, watch Wheel of Fortune and eat from a bowl of popcorn in which a spider is crawling around. The spider hunters are looking for a warm, dark, musty place where there are no other spiders around (since they're cannibals and the queen wouldn't let anything near the egg sac). They find Irv and Blaire dead and a spider emerges on Irv's face. Ross and Chris realize that the central location for all of this would be Ross' own house. Atherton and the Sheriff are already at Ross' barn. Atherton sees a mouse caught in a web and tweaks a long strand. A giant spider leaps at him and makes vampiric puncture wounds.
Dilbert comes to the barn with his poison and finds Atherton wrapped and dessicated. Meanwhile Chris and Ross enter the house. They find Ross' family watching tv as spiders begin to fill the room, climbing on the tv screen and over Michael J. Fox's face. They all run upstairs to the bathroom and out onto the roof to escape, but Ross gets trapped and falls through the floor below into the cellar where the egg sac is. He swings a shovel in panic and accidentally throws a spider onto the electrical panel where it burns up. He pours cognac on the egg sac but the appearance of a giant spider makes he fall into wine racks. Temporarily pinned, he throws bottles at the approaching spider and finally sprays fire, but the monster attacks out of a duct. He catapults it into the flames, but it flies again at him. This time he spears it into its own egg sac where the entire brood burns up. Dilbert pulls him out.
The closing scene has Ross and his wife Molly living in San Francisco and not much minding earthquake tremors.
Commentary: There are successful aftereffects in terms of weirding out people. Again, though, since the spiders don't seem to be symbolic of anything, the film can only worsen arachnophobia proper and this is less than desirable as insects grow more and more out of control these years.