Within the winding streets of Radiator Springs, Mater Larry the Cable Guy has been pulling pranks that ripple through the town. He moves Red's flowers, bursts out from a pile of tires built to resemble the Colosseum to startle Guido and Luigi, and even dresses up as a cone-wearing vampire to scare Sally Bonnie Hunt. He also tries to wake Lizzie Katherine Helmond while she sleeps, though that particular scare falls flat, and he moves Fillmore's gas cans back outside just as he takes them in. He also spooks Lightning McQueen Owen Wilson when Lightning believes Mater is hiding behind a stack of cans—only to discover it’s one of Mater’s signs.
To add a dash of legend to his mischief, Mater teases Lightning about the Ghostlight, a Route 66 urban legend. Sheriff Michael Wallis admonishes him for mocking it. When Lightning asks what the Ghostlight is, Sheriff explains that it is a blue paranormal orb haunting Radiator Springs. Mater counters that it isn't real, but Sheriff insists that the tale is true. He then recounts the disappearance of a young couple who encountered the Ghostlight, leaving behind two out-of-state license plates, and notes that it hates the sound of clanking metal. The moment hits Mater with fear, and he starts making the very noise the Ghostlight dislikes as he tries to quiet himself. Sheriff finishes with a caution that the Ghostlight could be anywhere. The residents say goodnight and turn off the store lights, leaving Mater nervous and alone in the darkness.
Nervous, he returns to his junkyard and spots a shadow that he initially interprets as a monster. He shines his light, only to find it's just a pile of junk with another one of his signs. A broken headlight follows as fear peaks, and he retreats into his wall-less garage as the door collapses. A light appears before him, and he panics, thinking it is the Ghostlight, until he realizes it's a simple lightning bug. He notices a blue glow behind him, checks it with a mirror, and bolts, certain that something otherworldly is chasing him.
Mayhem erupts as Mater is pursued by the Ghostlight, only to discover that the blue lantern trailing him is actually a lantern attached to Mater's towing cable, set up by Lightning and Guido. He wakes Frank and his tractors and races through Willy’s Butte, yelling in slow motion in a moment that echoes Doc Hudson’s famous slide. The town watches as Mater bolts around with the Ghostlight on his tail, until he tires and the group reveals it was a prank meant to pay back his own trickster ways. Sheriff gently reminds Mater that the only thing to fear on Route 66 is his own imagination. Doc Hudson jokes that the real fear is the Screaming Banshee, before the group parts and leaves Mater alone with his specter of fear.
In a post-credits moment, Mater actually crosses paths with the Screaming Banshee, a massive monster truck-construction vehicle with a broken windshield and a "BANSHEE" logo on the front, on the road. Unaware it’s him, he warns the looming vehicle of danger and heads back to his junkyard, leaving the enormous machine puzzled and the highway quiet once again.
