Teenager Carol Flynn and her boyfriend Mike go out searching for Carol's father after he doesn't come home one night. They encounter a giant spider in a cave near the man’s wrecked car. When the kids come back with the sheriff, the spider is seemingly killed by DDT, and its body is then stored in the local high school gymnasium. A teenage rock and roll band starts rehearsing in the gym, and their loud music revives the arachnid, which sends it rampaging through the town.
Carol and Mike go back to the cave to look for a bracelet that she dropped (the birthday present from her father). The over-sized arachnid then returns to its lair and the sheriff dynamites the cave entrance, unwittingly trapping the two teens inside with the spider. Rescuers open a small hole above the cave and send down a device that the teens use to electrocute the spider.
- Ed Kemmer as Professor Art Kingman
- June Kenney as Carol Flynn
- Eugene Persson as Mike Simpson
- Gene Roth as Sheriff Cagle
- Jack Kosslyn as Mr. Fraser
- Merritt Stone as Jack Flynn
- Sally Fraser as Helen Kingman
- Hank Patterson as Hugo
- Parts of the movie were filmed on location at Carlsbad Caverns. Other parts were filmed on a sound stage with matte effects to make it look like Carlsbad Caverns using a variety of scenic photographs. Bronson Canyon was also used.
- The last of Bert I. Gordon's "giant special effects" features from the 1950s. He would not do another until 1965's Village of the Giants.
- Special effects artist Paul Blaisdell had created a small makeup appliance ("about the size and weight of a postage stamp") meant to go on the live tarantula's back to make it look like it had "eerie, catlike" eyes, but this was never used.
- In one scene, a teenager is seen with issue #1 of the magazine Famous Monsters of Filmland.
- During a scene where Mike his shown working at his father's movie theater, he refers to Attack of the Puppet People, another film directed by Bert I. Gordon.
- In 2001, a made-for-TV movie starring Dan Aykroyd was produced entitled Earth vs. The Spider. It has no narrative or thematic connection to this film beyond the main character having the last name "Kemmer".
- A brief scene of the spider's rampage was seen in the 2002 Disney animated feature Lilo & Stitch.