Richard (Judge Reinhold) is taking his wife Beth (Julia Sweeney) and their two children cross-country in a recreational vehicle to a family reunion. Richard wants this to be as special for his children as an RV trip he took as a child with his family was for him. He has even purchased a DVD of the same movie he watch on his childhood trip, The Shakiest Gun in the West. But two things go wrong right off (in addition to his wife being mad at him for exceeding the budget on the RV he rented). First of all, while he was gone to rent the RV, his brother called and ask if Richard and his family would bring something to the family reunion for him and Beth agrees without understanding what they are to bring, only that it is being shipped to their house. It turns out to be Beethoven, a large but lovable Saint Bernard. The second problem is that the DVD Richard purchased does not have The Shakiest Gun in the West on it, it instead has a secret computer code which a delusional genius and has idiot partner stole and hid on the disk. The two inept crooks learn where the disk is and follow the family looking for an opportunity to steal the disk. The only thing stopping them is Beethoven, but since no one else, except the young girl, ever sees them it looks like the things Beethoven does to stop them are just more bumbling messes which get Beethoven in more trouble with the family.
 As with the other Beethoven movies, this movie was a lot of fun and is sure to be a hit with the same children (and adults) who enjoyed the earlier Beethoven movies.