The Flynn-Fletcher family are in their RV on their way home, and Candace complains that she couldn't call her friends because of the "spotty connection". She tells Phineas and Ferb that she's glad they didn't build anything during the trip, but they didn't pay attention because they were zoning out after Candace said that they didn't get to go to a truck stop diner. As Candace decides to sleep on a couch, Phineas tells Ferb that he knows what they are going to do and notices an inflatable Perry, mistaking it for the real Perry. The real Perry slips through a secret entrance and gets a briefing from Major Monogram who mentions that Doofenshmirtz is driving a rig not far from his location and tells Perry to investigate him. He expresses how he's envious of Perry for going on a trip. Perry then goes under the RV to the engine and uses his laptop to hack into the GPS to reroute the RV.
Meanwhile, Lawrence decides to use a CB radio to talk to truckers and goes as "Cheeky Monkey". He uses truck slang to talk to truckers and shows Linda how he learned to speak truck slang in "Truck Driver Hits, 1975 to 1975". He gets one of the truckers with the nickname of "Misfortune" which turns out to be Dr. Doofenshmirtz, who is having a hard time talking in truck slang. While Doofenshmirtz is talking to Lawrence, Perry jumps across to Doofenshmirtz's truck and after seeing Perry he cuts him off. After talking to Doofenshmirtz, Linda tells Lawrence that he scored some big man points.
Doofenshmirtz tells Perry not to attack him since he is driving and presses a button to tie Perry up with a seatbelt. He explains to Perry that all his Inators need a formula that scientists call "Boom Juice" for the self-destruct sequence. He manages to find a cheap price and has to drive it back home and decides to talk to Perry about truck driving tales.
Meanwhile, Phineas and Ferb are getting their seatbelts on and gathering their tools as their chair went up to the roof of the RV, and Candace goes sleep-walking to go bust Phineas and Ferb. Lawrence and Linda are listening to the Truck Driver Hits on the radio about some truck driver saving Christmas and sees Candace sleepwalking. Linda says, "Honey, Candace is sleep-busting again.", and sends her back to the couch and continues to listen the radio about a group of truckers taking down some corrupt cops. At the same time, Phineas and Ferb receive a trip delivery for the diner food and wonders if they are too young to order this and Phineas states that the age is not an issue there.
Doofenshmirtz is still talking about truck driving tales while Perry escapes by getting a nickel from the seat to toss to a side-mirror to reflect the sun and uses a magnifying glass to burn the seatbelt and then tackles Doofenshmirtz to take control of the rig. However, Doofenshmirtz fights back and uses his Hitch-A-Ride-Inator to connect the Flynn-Fletcher RV so that they can drive his rig for him. After they battle each other, Lawrence notices Doofenshmirtz as a pharmacist who is putting his face in the windshield and comments that Americans are like big children.
As Candace wakes up and sees her brothers aren't seen in the RV, she goes to her parents and asks if Linda's seen them, but Linda thinks she's still sleep-busting and sends her away. Candace then notices the music and goes to the roof of the RV and enters in the "No Stop Truck Stop". While Candace is nagging Phineas and Ferb about doing this during the last days of their trip, she unintentionally blooms into the role of a waitress after she hears some customers with their orders.
Meanwhile, Doofenshmirtz and Perry are fighting at the top of the rig. Doofenshmirtz uses a lid to throw at Perry, but it bounces off a sign and hits him and falls off than it bumps his rig which affected the RV. It shook the laptop to disconnect the GPS, which tells Lawrence to turn left to a corn field. Lawrence does so, thinking that it is a shortcut. Perry notices they are heading toward Cactus Gorge, jumps towards the Hitch-A-Ride-Inator, and turns his fedora into a buzz-saw to cut the Inator to separate it from Doofenshmirtz's rig as it heads toward the gorge that Doofenshmirtz also jumps out from. Perry quickly fixes the GPS and the laptop to reroute the RV to prevent it from plunging into Cactus Gorge. Doofenshmirtz runs toward his rig and sees it falling in Cactus Gorge and it explodes.
The shockwave of the explosion causes Candace to fall off the escalator to the roof of the RV and falls to the seat that goes up and quickly grabs Phineas and Ferb talking to customers about truckers banding together to save Christmas. Linda goes to check on the kids and sees them sitting together, and Candace tells her to go to the roof to see the diner that Phineas and Ferb built. At the same time, the farmer and his wife are at the overpass talking about their dreams and the wife comments that she wants to own a truck stop diner. The Flynn-Fletcher RV passes the overpass that the diner stops at and was right behind them. Linda goes to the roof of the RV and sees nothing on it, leaving Candace to cry out in despair. Lawrence joins them and they gave him a stare when he realized that no one is driving the RV.
After having his pants burned by the explosion Doofenshmirtz states that he needs a new pair of pants and he says that it couldn't possibly get any worse, prompting many flaming cactus to fall on top of him.