Valentine "Val" McKee and Earl Bassett work as handymen in Perfection, Nevada, an isolated ex-mining settlement in the high desert east of the Sierra Nevada mountains. When they eventually tire of their jobs and choose to leave, they find the earth infested with gigantic man-eating wormlike creatures that live below and the slightest vibration of the ground can endanger their very lives.
A man on an oil field in Chiapas, Mexico flees from an underground creature which emerges and eats the man, revealing it to be a graboid. Years after the events of Tremors (film), Val McKee has moved away and married Rhonda LeBeck, while Earl Basset has squandered his fortune on a failing ostrich ranch. He is approached by Carlos Ortega, who informs him that graboids are killing his workers at his oil field in Sonora, Mexico, and hires him to hunt them down. Earl initially declines, but Ortega's taxi driver, Grady Hoover, convinces Earl to change his mind; both join the hunt. Upon arrival in Sonora, Earl learns that the company would pay him double if he caught one of the creatures alive. He also meets geologist Kate Reilly and her assistant Julio, who are scientifically investigating the Graboids.
Adventurer Burt Gummer returns to his hometown of Perfection, Nevada, after a hunt for Graboid in Argentina. Since Tremors (film), the town's preventative equipment for tracking Graboid activities has fallen into disrepair due to the neglect of native residents Miguel, Nancy Sterngood, and her daughter Mindy. Walter Chang's market has been taken over by his niece Jodi, and the town has gained a new resident, Jack, who creates mock-attack tours for visiting tourists. One afternoon, during one of Jack's tours, his assistant Buford is eaten by an actual Graboid. Jack, Mindy, and Jack's customers manage to escape to warn the town, and Burt determines there are three Graboids in the area.
This spin-off of the Tremor movies chronicles the town of Perfection, Nevada, which has a little problem with great big worms. The Graboids, and their offspring the Shriekers and Ass-Blasters, have overrun the valley but are on the government's protected species list. The locals are (barely) allowed to live there rather then leave their homes, as long as they don't harm the creatures, particularly the giant Graboid known as "El Blanco." Complicating matters, a secret government lab accidentally unleashed a gene-blending substance called "Mixmaster" into the area, occasionally causing various animal-types to recombine into new monsters. The natives of Perfection include survivalist Burt Gummer, 60's hippy-type Nancy Sterngood, and grocery store owner Jodi Chang who all try to make a living. New to Perfection is tour guide Tyler Reed and Rosalita Sanchez, a mysterious woman with a past. Government representative W.D. Twitchell keeps an eye on the whole situation.
In 1889, the inhabitants of Rejection are completely dependent on the income from a nearby silver mine. One day, a hot spring causes graboid eggs to hatch, resulting in the death of 17 miners. Hiram Gummer, great-grandfather of Burt Gummer (Michael Gross (actor)) and the mine's owner, arrives in town to fix the problem. After juvenile graboids that can shoot out of the ground (later later dubbed Dirt Dragons) attack his camp one night, he is shocked by their presence. One of his companions, Juan, kills one with a pickax, and the pair escapes.
Burt Gummer, now a star in his own survivalist series, and his new cameraman, Travis Welker, are approached by South African Wildlife Ministry agents Erick Van Wyk and Johan Dreyer, who hire them to deal with Graboid#Ass-Blaster in South Africa.
In Canada's Nunavut, a team of young researchers collecting ice core samples of glaciers is attacked by a Graboid. After brushing off a tax agent, Burt Gummer and his son Travis Welker are asked by Dr. Rita Sims and young Graboid hunter Valerie McKee to investigate. Their plane is attacked by an Graboid#Ass-Blaster, but Burt and Travis make it to the facility. They learn that Arctic heat conditions have made the area prime for Graboids. Burt suspects their research neighbors at DARPA are developing bio-weapons out of the Graboids. When an Ass-Blaster attacks the facility, Burt rescues a researcher but experiences an episode and collapses. He learns that he has been infected by a parasite based on Graboid venom, and that they need to extract the antibodies from a live Graboid.
When a group of hunters genetically modify Graboid eggs, they face an all-out war against the larger, terrifyingly intelligent Graboids, and the swiftly multiplying Shriekers.
