Instead of flying to Florida with his folks, Kevin ends up alone in New York, where he gets a hotel room with his dad's credit card—despite problems from a clerk and meddling bellboy. But when Kevin runs into his old nemeses, the Wet Bandits, he's determined to foil their plans to rob a toy store on Christmas Eve.

On Christmas Eve, divorced dad Scott Calvin and his son discover Santa Claus has fallen off their roof. When Scott takes the reins of the magical sleigh, he finds he is now the new Santa, and must convince a world of disbelievers, including himself.

When a doubting young boy takes an extraordinary train ride to the North Pole, he embarks on a journey of self-discovery that shows him that the wonder of life never fades for those who believe.