Along a two-lane highway in the Northern Arizona desert, four cars stop for lunch at the Apache Acres restaurant. Driving a pink, boxy economy car are the newlyweds Rollie and Lollie, who have not yet consummated their marriage. Driving a gray Volvo station wagon are the Briggs family, father, Stuart, mother, Barbara, and adolescent son, Howie. Driving an orange Camero sports car are the young record producer, “Crush,” and three female backup singers, Faith, Hope, and Charity. Driving a vintage light, green sedan is businessman Sidney Preston. While the other patrons look at the menu, Sidney orders chili, but after taking a few bites collapses to the floor. Tugger, the cook and restaurant owner, offers to telephone for an ambulance, but Sidney says there is not time. As the patrons gather around, Sidney tells them $4 million is hidden in four different places, $1 million in each location. Each one is hidden in a bridge, but he dies before he can reveal anything more. As the patrons ponder the cryptic clues, they notice a television news report announcing that former White House aide Sidney Preston has disappeared with $4 million in illegal payoffs from the Libyan government. The report shows a photo of Sidney, saying he was born in El Puente, Arizona, and is believed to be hiding somewhere in the state. Tugger says that El Puente is only an hour west of the restaurant and young Howie reports that “puente” means “bridge” in Spanish. However, waitress Dotty informs them that there is no bridge in El Puente. As the other patrons consult maps trying to figure out where to find the money, Dotty pulls Tugger aside, announcing that she used to live in El Puente and there is a bridge there. She lied to give them a head start on finding the money. Meanwhile, FBI agents Fred and Bob drive down the highway and spot Sidney’s vintage car parked in front of Apache Acres. They pull into the parking lot just as Tugger and Dotty drive off in a pick-up truck toward El Puente. The other patrons see Tugger’s truck speeding away and rush to their cars to follow. When Fred and Bob go into the restaurant, they find Sidney’s dead body and notice a map with El Puente circled. As the cars race down the highway, Tugger decides it will be faster to cut across the desert rather than follow the road. However, as he attempts to drive up a steep hill, his truck tips onto its side. A man named Slaughter arrives in a truck and attaches a cable to the pickup’s bumper. However, after the truck is right, the bumper breaks and the truck rolls backwards over a cliff. Tugger and Dotty fill Slaughter in on the $4 million quest and persuade him to give them a ride. Meanwhile, Barbara Briggs wonders if the race to find the money is worth the trouble. Stuart informs her that he bought 50,000 shares in a failing car company and they are now broke. As Stuart swerves to avoid something, his station wagon careens into a small pond in front of the High Plateau Refinery. The Briggs get out of the vehicle easily, but the car begins sinking into the pond and rapidly disintegrates, and they realize the pond is filled with toxic waste. The Briggs walk down the highway when a Winnebago motor home stops to help. The vehicle’s owners, Bad Boris and Awful Abdul, refuse to let them get in because they smell bad. But after the Briggs offer to share the $4 million they are chasing, they are welcomed into the Winnebago. Meanwhile, a police officer pulls over Crush’s Camero. When Crush does not have his driver license, one of the girls moves into his seat, pretending to be the driver. However, Officer Gretchen is wise to what they did and arrests all four. At the jail, the girls flirt with Officer Quinn to get the jail keys from him and escape. Meanwhile, Rollie and Lollie pull into a “thirty-minute” motel so they can consummate their marriage. However, the room has a Murphy bed and Rollie gets stuck in the wall when the bed springs back up. Later, all the vehicles arrive at the El Puente footbridge at the same time. They find a bird’s nest with fifteen eggs in it. Thinking that they’ve been led astray, Slaughter throws an egg into the canyon below. However, the others notice that words are written on the remaining eggs. They put them all together to discover a clue that reads, “It’s Very Close So Please Don’t Gripe, The Money You Seek Is In The . . .” The final word of the clue was written on the broken egg. Howie suggests the word is “pipe” since it rhymes with “gripe.” They look under the bridge and see a large pipe with a briefcase inside. Slaughter climbs down to retrieve it, but the handle breaks just as he pulls it out and the briefcase falls to the rocks below. It comes open and all the money is scattered by the wind. The treasure hunters wander through town looking for more clues. Howie notices a newspaper with a front-page story about Sidney Preston’s death that mentions he lived on a houseboat docked at the Lake Powell Marina. Stuart suggests the money is hidden in the bridge of the houseboat and everyone takes off for Lake Powell. However, before they leave, Howie tells his parents they are setting a bad example for him and he hitches a ride to the lake with Boris and Abdul. His parents are not worried, believing everything will be fine once they are millionaires, and steal a car to get to the lake.
Slaughter’s truck will not start, so he, Tugger and Dotty steal a fire truck that has just driven up to put out a fire in an office building. When Crush and the girls stop for gasoline, they notice Officers Quinn and Gretchen also getting gas. Crush attaches a tow truck line to their police car. When Quinn and Gretchen give chase, the rear end of their police car is torn off. Nonetheless, the officers keep going and finally stop Crush’s car. When Crush and the girls tell them about the $3 million still to be found, the police officers are happy to join their quest. With both cars inoperable, Quinn and the rest hijack another car at gunpoint. Meanwhile, Rollie and Lollie stop to have sex in the desert and their car rolls away. Arriving at the marina at the same time, they find Sidney’s boat docked in slip number seventy-five and inside the boat notice an aquarium with a small bridge decoration. They pull the bridge out looking for a clue and find the money hidden in a plastic bag underneath the aquarium rocks. They open the bag, but someone accidently presses a button that opens a chute sending the money into a paper shredder. The money is gone. Meanwhile, Howie plays a video game on Sidney’s computer and a screen appears which reads, “Here’s Another Clue: 8B261.” No one is sure what the clue means until they notice a billboard advertising the relocated London Bridge in Lake Havasu City, and decide that is where the money must be. When they return to the parking lot, their vehicles have been towed away. So, Fred and Bob attempt to confiscate a small plane, but a hijacker tries to take it to Tijuana, Mexico instead. Crush and the girls hijack a tour bus filled with Asian tourists who do not speak English. Rollie and Lollie steal a truck. Slaughter, Tugger and Dotty steal motorcycles from a biker bar. Boris, Abdul and the Briggs hire a hot air balloon. Despite mishaps along the way, everyone arrives at London Bridge at the same time. As they search, the balloonist explains that the bridge was taken apart in London, England, then shipped to Arizona and rebuilt. Each block was individually numbered to facilitate its reconstruction. Howie realizes that the 8B261 clue must refer to the block number. They find a portable lock box hidden behind that block, but the balloonist grabs it and takes off. Once airborne, the balloonist holds up the lock box for all on the ground to see. However, the lid comes open and the money scatters into the lake. Boaters and swimmers grab the money. Despondent treasure seekers realize that $1 million is still hidden somewhere. Just then, a riverboat named “Bridge Over Troubled Waters” rides by and everyone rushes to get onboard.