When Denby, an abandoned golden retriever, is rescued by Santa in the Nevada desert on Christmas Eve, he knows he has found the perfect family. But over the months between one Christmas and the next, Denby finds himself again and again doing what he has been told not to do. Is it magic? Are his actions somehow tied to the injury he had when Santa found him? Or is he just a bad dog? With the help of a reindeer, some elves, and Santa himself, Denby finds that solving his own mystery could also mean saving Christmas.