Scott Calvin is disgusted to learn that his ex-wife, Laura, and her husband, Neil, have tried and failed to break it easy to their 6-year-old son, Charlie, that Santa Claus isn't real. On Christmas Eve, Scott reads "The Night Before Christmas" and then receives an unexpected visitor on his roof. When Santa is startled by Scott's calling out and falls off, he disappears, leaving only an 8-reindeer sleigh and a suit with instructions to put it on if he's involved in an accident. Scott does so and is transported around the town dropping gifts through chimneys until he's taken to the North Pole and informed by a group, who claim they're elves, that he is now Santa. Charlie is proud of Scott's new job, though he's convinced it was a dream. Then his hair turns white, his beard refuses to stay shaved, he gains weight inexplicably, and he has a sudden love of junk food. Now he's accepted it, there's just one problem: how to keep it a secret from his disbelieving family.