Coop, Jamie, and Kiva are headed towards Santa Fe New Mexico, for the Santa Fe Chili Con Cookoff. A contest where participants must use chili in their recipes. Coop had originally planned for it to just be him & Jenna, but at the same time. His mother and Aunt Ester were going on a spa weekend and someone needed to babysit Skippy. Jenna volunteered.
Along the way, the gang stop for a snack break. Coop breaks out the bowl of chili he made for the contest and offers some to Jamie & Kiva. Jamie refuses as he likens the chili to "hot death". Kiva tries a bite, but she immediately spits it out due to how spicy the chili is. She drops her bowl of chili, causing it to seep into the cracks of the desert ground. Unbeknownst to the gang, there is a huge tunnel system underground. There are gigantic mutated earthworms that reside below. The chili drops on them, waking them up.
Before the gang can continue their way to Santa Fe, the ground is ripped up. A giant mutated worm attacks Megas and drags it underground. Megas manages to defeat the worm, which runs away. Jamie says they should leave it alone, but Coop and Kiva want to go after it, the latter stating that if there are more of these things, they could cause trouble to populated areas.
Meags travels through a giant underground tunnel system. Kiva is impressed how intricate and complex the sprawling tunnels are. Among their travels, they discover a pile of bones, which belong to various creatures, including those of humans. Jamie pleads to the others to forget the giant worm, but both Kiva and Coop want to stop it. They tell Jamie that he could have stayed home to watch Skippy instead. Jamie says he' d rather take the worms than Skippy anyday.
The gang stumble upon a community of mutated Earthworms. Megas fights with the worms multiple times. After destroying a wave, Kiva reveals that there are even more further underground. Megas continues traveling through the tunnels, destroying more worms as they go. Coop starts to side with Jamie considering he is using Megas as a heat source for his chili and doesn't want to over do it. Kiva insists that they care of these worms first.
Megas then gets ambushed by another wave of worms. They manage to trap Megas in a webbing cocoon and drag it way to a spawning chamber. It is there that there are more worm eggs, which will hatch into more giant worms. The worms plan to fee Megas to their queen, a gigantic bloated worm. Megas manages to break free and fights the worms some more.
Megas continues traveling through the tunnels while being chased by the queen and the worm army. It is then revealed that the worms have grown to a giant size due to there being a toxic waste dump underground. Kiva has Megas soak up the waste so it can be disposed of later. Kiva then says they need to destroy the queen and the rest of her army.
Megas continues to fight against the army, along with the queen. Eventually, Megas makes its way back to the surface. Megas plans to fire acid at the queen, but instead fires the toxic waste it just took in. This causes the queen to mutate even further. Megas gets ravaged by the queen. The queen then notices Santa Fe in the distance, and makes its way there.
Megas continues to fight against the queen and her army. Eventually, the army is destroyed, but the queen remains. Megas has trouble dealing with the worm queen. Coop then has one more trick up his sleeve. He fires a huge pot of chili at the queen. She eats it and burns up. Coop defeats the queen, but lost his chili in the process. The contest starts in about 3 hours, so Coop decides he will whip up a fresh batch of chili.
The end credits show the judge eating Coop's chili. He gets a severe case of heartburn and nearly dies. However slowly gets up and places the blue ribbon on Coop's chest. Coop wins the chili contest.
