My Grandfather's annual sundowning episode is coming tonight.

My Grandfather lives independently on the North Pole and general does very well with the help of Grandma and about 100 diminutive aides. But every year on December 24th, he has what I can only call a "sundowning" episode. First, he has his aides load millions of toys on his homemade sleigh. Then he rounds up about 8 reindeer (9, if he can find the one with the weird red nose). He hitches them up to the sleigh and whistles and shouts and calls them by name, and off they go. We have no idea where he goes or why, but by morning he is back and the toys are all gone. I've tried to tell him that he's too old for this kind of thing and he shouldn't be driving, but he won't listen. It's making me crazy and I don't know what to do. Any suggestions?