In a small town, an oil company is drilling for oil. The geologist, Dowd, informs his boss, Tenneson that they detected what could be an ecosystem which could affect their drilling rights. But Tenneson tells them to go on and something happens. Something came out and Tenneson wants to keep it quiet by keeping what came out on ice. In the town, something’s been taking the fuel tanks off vehicles, leaving a big hole. Tripp, who lives in the town is frustrated at his life, specifically not having a vehicle of his own. He works at a scrap yard and he’s been working on restoring an old truck. One day he thinks he hears something and traps it in the storage pit. He calls the Sheriff who’s his step-father, whom he doesn’t like. And when he gets there, it’s gone. Later he sets a trap for it and sees it’s a slug like creature who feeds on oil. He would bond with it. Later a man from the oil company shows up at the yard and asks him about the thing he reported earlier. Tripp feigns it was mistaken but the guy doesn’t believe him. The creature enters the chassis of the truck he was working on and makes it move. He then gets in the truck and it goes off on it’s own and he tries to figure out what to do.
The film opens at a oil well for Terravex, an oil company. CEO Reece Tenneson (Rob Lowe) goes to the well and talks to Dr. Jim Dowd (Thomas Lennon) since this well is not pumping oil. As they investigate the blockage, another scientist discovers a water pocket below the earth that may indicate the possibility of an ecosystem living down there. The water pressure then starts to destabilize. The well bursts and three monsters pop out.Tenneson hires a man named Burke (Holt McCallany) to capture the monsters. Two are taken in but one of them has escaped and is hiding inside a truck.We meet high school student Tripp (Lucas Till). He lives with his mom Cindy (Amy Ryan) and her boyfriend Rick (Barry Pepper), who is the town's sheriff. Tripp wants nothing more than to get out of town and do something on his own. He works as a mechanic for Mr. Weathers (Danny Glover), who has brought in the truck that the missing monster is hiding in.At night, Tripp goes into the garage to mess around with a truck that he wants to fix up. He sees a news report with his estranged father Wade (Frank Whaley) reporting from near the oil well after witnessing the incident from the previous night. Tripp then hears a noise and sees one van in the garage with a hole where the gas tank used to be.At school, Tripp rides his bike and talks to Meredith (Jane Levy), a girl in his class who is supposed to tutor him. He then runs into his friend Sam (Tucker Albrizzi), and they see people gathered around another car with a hole in the gas tank.In the garage at night, Tripp hears a growling noise by the oil canisters. He encounters the missing monster and hides in the cellar before trapping it in there. He calls for help, leading to Rick and some of his men to come by an investigate. However, the monster is gone when they look in the cellar. Rick accuses Tripp of lying to cause trouble.The next night, Tripp gets some oil canisters to lure the monster out. The monster makes its full appearance as a large, squid-like blob. It starts to feed on the oil but then nearly gets crushed under a compactor after Tripp drops the switch and it breaks. Tripp pulls it out in time. Although a bit hostile at first, the monster warms up to Tripp, and they start to have fun by throwing things at the Terravex truck.Burke goes to the police station to ask around about the monster since it was reported as being spotted. Both he and Rick butt heads over their concerns regarding the monster.Tripp tries to keep the monster hidden from everyone. Burke comes by the shop asking questions, though Tripp denies that he's seen what Burke and his goons are looking for. After getting them out of the garage, Tripp finds Meredith coming by as she was looking for him but came walking. She asks for a ride home, but Tripp tells her he can't take her. When the monster, who is hiding in Tripp's truck, starts growling and making noises, it arouses the suspicion of Burke. Tripp gets Meredith and hops in the truck so they can get out. Burke and his men start following them, and the monster starts to take control of the truck to get them away from the villains. Meredith sees the monster, which Tripp has decided to name Creech. She's freaked out at first but then sees that Creech is harmless. She lets Tripp hide Creech out in a stable near her house.Dowd has been doing research on the other two monsters. He determines that they feed off oil and that they are quite intelligent.Tripp and Meredith have fun with Creech as Tripp decides to use him as an engine for the truck. Tripp modifies the truck to fit Creech and to keep him hidden. He and Meredith take Creech out and stop for gas. However, since gas has more chemicals than regular oil, Creech goes wild and starts riding like crazy through town, causing lots of damage to other cars and destroying an entire lot of cars by riding over them.Back at Terravex, Dowd continues to research the other two monsters, and has even developed an affection for them. Tenneson says that they plan to poison the well that the creatures came from.Tripp and Meredith stop by where Wade works. Tripp tries to talk to him about his situation, but Wade instead sells them out to Burke. When Burke threatens Tripp to give up Creech, the monster takes control of the truck. Tripp and Meredith hop in, and Tripp has Creech ram through Wade's trailer. Burke and his goons chase after them, while Rick is in pursuit after they ride into town. Creech manages to climb up the walls and sneak over Rick to avoid detection. The gang hides out near Meredith's house for the night.In the morning, Creech is gone. Since Tripp left his phone in the truck, Meredith uses an app to track it. It leads them to Terravex. They find Creech has reunited with the other two monsters, who turn out to be his parents. Tripp and Meredith get caught while the monsters are captured, and Tenneson erases any trace of the monsters from their phones. Dowd escorts the two out of the building, but he tells them he wants to help them because he cares about the monsters.With help from Sam and Mr. Weathers, Tripp gets two more trucks that he and his friends fix up to accommodate the monsters. They take the trucks back to Terravex and break out Creech and his parents. Tripp, Meredith, and Dowd ride toward the oil well above the monster ecosystem as Burke and his goons follow them. Rick gets in on it too, but Burke rams his car down a hill. Rick then gets inside a larger vehicle to run Burke's goons off the road. The three trucks make it to the oil well, but the workers have already started to drill down with the poison. Burke tries to push Tripp and Creech into a hole, but Creech grabs Burke's truck and flings it into the drilling machine, ceasing the poisoning. Tripp and Creech fall into the hole but land in water. Creech pulls Tripp out of the truck. Tripp sees the rest of Creech's family as he and his parents rejoin them. Tripp says goodbye to Creech.Tenneson and his cronies are arrested for their dirty deeds. Tripp and Rick are now on good terms and have fixed up the truck to make it look better. Tripp and Meredith then go for a ride through town.