For the Duncan family, Christmas is about to take a major detour.

Teddy Duncan's middle-class family embarks on a road trip from their home in Denver to visit Mrs. Duncans Parents, the Blankenhoopers, in Palm Springs. When they find themselves stranded between Denver and Utah, they try to hitch a ride to Las Vegas with a seemingly normal older couple in a station wagon from Roswell, New Mexico. It turns out that the couple believes they are the victims of alien abduction. The Duncan's must resort to purchasing a clunker Yugo to get to Utah, have their luggage stolen in Las Vegas, and survive a zany Christmas with Grandpa and Grandma Blankenhooper.