There are only two types of people that drive down the dusty highway of Pueblo, New Mexico: truckers or businessmen who are simply passing through. But that suddenly changes one evening when a mysterious trucking accident knocks out the phone lines and blocks the only way out of town, thus leaving Pueblo in complete isolation.

Early next morning, Sheriff Annie is summoned to investigate the mysterious deaths of scores of cattle whose carcasses have been disfigured beyond recognition. Realizing that this is probably not the work of coyotes, she continues to battle her daily hangover and makes her way over to the site of the trucking accident. When she arrives at the wreck, she finds another horrific scene: a scorched big rig with only the limb of the driver remaining. But Annie takes note of one inexplicable clue - a strange, crab-like leg affixed to the front of the tanker's grille.

Elsewhere on the highway, a sweet teenager named Ally and her older sister Caya pull-off the road to help Charlie, a good-looking ranch hand whose car has died in the middle of nowhere. When the three arrive at the first and only gas station in Pueblo, they are greeted by Nodin and her Grandpa who informs them that not only is there no gasoline at the station, but the road out of town has been blocked. Hank, a traveling salesman who specializes in synthetic urine, isn't too happy to be stuck there either.

Soon after, Annie arrives at the gas station to speak with Nodin about her findings, as Nodin is a Native American who specializes in botany and plant DNA structures - the closest thing Pueblo has to a forensic scientist. After performing a few basic tests on the crab-like leg, Nodin determines that it is part of an unknown organic life form - nothing she's ever seen before.

As evening settles in, Ally decides to make herself useful and take out the trash. Alone outside, she is surrounded by the empty desert night. It's enough to give a girl the creeps! As she starts to head inside, she suddenly realizes that she is in fact not alone. The creature, who has just returned from a bloodbath at the local bar, rips her to shreds - tossing her torso back into the house. Now aware of their uninvited guest, some try to run for safety against its deadly force, as others are torn limb-from-limb in seconds.

As the deadly rampage continues, and as Annie's judgment weakens from her alcohol withdrawals, the group learns their only hope is to place their trust in an unlikely ally - a young Native American who not only unleashed the monster, but may be their only hope in stopping it.