When Milo accidentally joins another family on their vacation, the new family must learn to cope with Murphy's Law.
The Murphys depart for their family road trip, leaving Diogee in the care of Zack and Melissa. After seeing a number of sights - and going through a number of mishaps - the family stops at a gas station only to have Milo accidentally get into the RV of Mr. and Mrs. Brulee and their twin daughters. After discovering the mix-up, the two families agree to rendezvous, only for both to come across misfortune along the way due to Murphy's Law. While the Murphys take things in stride and his daughters actually enjoy the sights during delays on their way to the Grand Canyon, but Mr. Brulee is greatly distressed.
After numerous mishaps - and incidents in which various Brulee family members are forced to put money in jars for various offenses - the RVs of both families end up in a river. Fortunately, Diogee - whom had escaped the relaxing Melissa and Zack - arrives and manages to get both families to safety, though their vehicles are lost in the process. However, the Murphys remain calm, while the Brulees come to a newfound appreciation for more unique vacations.