Late on Christmas Eve, a young boy lies awake in bed doubting the existence of Santa Claus and nervously waiting to hear the sound of sleigh bells. Instead a magical steam engine roars outside his window, bound for the North Pole. The train's irascible conductor (Tom Hanks - in one of several roles) invites the boy on board, and together they begin a roller-coaster journey up mountains, across ice fields and beyond imagination.