Young Justin Carver (Dylan and Cole Sprouse) is having Thanksgiving dinner with his family, only for it to end with the news that his best friend Bobby's (Hannelius) bickering parents are finally deciding to divorce. When he overhears his own parents, Stephanie and David Carver (Sellecca and Bernsen) having a heated argument, Justin retreats to his bedroom. A few minutes later, Justin peeks downstairs, only to see his mother Stephanie locked in a warm, romantic embrace with none other than Santa Claus (his father in a Santa suit). He takes a photo, shows it to Bobby the next day, and then sends it to Mrs. Claus. Fooled by Bobby's own situation with his parents, Justin jumps to the conclusion that his mother is having an affair with Santa. So he decides to behave as badly as possible in an attempt to prevent Santa from coming to his house on Christmas Eve night for him to make off with Justin's mother. The resulting hi-jinks include Justin setting traps and throwing snowballs at a street Santa, and even getting himself in trouble at school. Then, on Christmas Eve, Justin's mother receives a letter from the post office. Inside is the photo, which didn't get sent. In the end, Justin finds out that Santa was his father and apologizes to the street Santa.