Shriekers are spotted in Juniper, Arizona and Twitchell sends Burt and Tyler to handle the situation. However, the Fish and Wildlife Service are also in town and manage to kill five Shriekers. They also take one alive for study and when it gets a hold of some food, the Shriekers start to multiply again. Now Burt and Tyler have to stop them from massacring the entire town.

Burt finds and kills a Shrieker in the valley, only to learn it was a part of a government funded project to train Shriekers for rescue missions. But when a storm knocks out the equipment controlling them, the remaining Shriekers escape and multiply. Now to survive, the Perfection residents must make a stand at Burt's place.

Burt rescues newcomer Tyler Reed from the government-protected Graboid known as El Blanco. It happens that Tyler is the new owner of Perfection's tourist business and he couldn't have come at a worse time. El Blanco is becoming more aggressive and the Perfection residents have to figure out why before they become the next meal.

Three people enter an abandoned silver mine and are attacked by a strange creature, which drains the water from their bodies. Rosalita thinks it's a ghost, but Burt knows it must be something else, especially when two government agents arrive in Perfection.

Larry returns to Perfection and wants to learn more about Cletus Poffenberger. Tyler tells him the story of when the Perfection residents first met Cletus and had to face his increasingly dangerous pet, Four-Twelve.

Twitchell sends Burt and Tyler to a small town on the belief a Graboid is responsible for recent disappearances people. But the townspeople believe the real cause for the disappearances are alien abductions and that the government is trying to cover it up.

A team of scientists find a deadly strange animal/plant hybrid growing in the valley. Burt, Tyler and Cletus work with them to figure out how to stop it before it spreads even further. Meanwhile, Perfection has to deal with an over-excited tourist named Larry.

Frank returns to Perfection with some help in another attempt to kill El Blanco and retrieve the key he swallowed. Meanwhile, Larry encounters a creature in a barn and tries to figure of what it is.

An Blaster has arrived in the valley, already having killed two people. After going out after it, Burt and Tyler learn the AB is private property and must be taken in alive. Meanwhile, Jodi and the others take over teaching Burt's survival class.

Two Las Vegas criminals named Max and Frank have to lay low before their next crime. With time on their hands, they go to Perfection to settle a disagreement about the existence of Graboids. They soon enough encounter El Blanco, which kills Max and also eats the key needed for their crime. And the only way to get it back is to kill El Blanco.

The valley has an infestation of strange bugs that make loud noises when they are about to feed. They start eating dry wood, but soon enough they move onto meat and begin making their way toward the town. Meanwhile, Larry has decided to move into town.

Residents of Perfection are facing money troubles and Rosalita decides to take a job at Melvin's latest business venture, the Oasis. But some of the water Melvin uses for the Oasis' lagoon actually came from Perfection and contains Mixmaster, creating a deadly six foot shrimp. And when Melvin's attempt to kill it drives the shrimp out of the lagoon, Tyler and the others will have to stop it before it escapes into the wild.

Protesters come to Perfection to force Burt and the others out of the valley, claiming their presence is badly affecting El Blanco's health. This leads to an awkward family reunion when Mindy is apart of the protesters. Even worse, El Blanco begins acting strangely.