A younger resident of Grand Rapids, Michigan, born sometime around 1950, he is of an age where he must decide once and for all whether he still believes in Santa Claus, but is very much afraid of being the last in his circle of friends to hold to this belief, and seeming foolish.The movie shows him to be studying the problem from a rational angle, including studying the hard scientific facts about the inhospitable nature of the North Pole, and the famous Saturday Evening Post cover by Norman Rockwell showing a young boy finding his father's hidden Santa outfit. Part of him obviously still wishes to believe.
This conflict comes to a head when he hears and sees the impossible: a train appears in his house's front yard, where a conductor beckons and then impatiently waits for him to get on board what he describes as The Polar Express, for a trip that will end at Santa's workshop. While afraid, he climbs aboard, befriending the very optimistic and courageous girl, as well as the enthusiastic but annoying know-it-all kid and a lonely boy who seems to think his family's poverty makes him unworthy of their friendship or Santa's generosity.
Attempting to aid (and he mistakenly believes, rescue) the girl, the boy falls into several mishaps and adventures. He ends up riding on the roof with what seems like the ghost of a hobo who failed to duck in time to save his life. He wanders into a storage car full of marionettes, who, in the dark seem to come to life and taunt him. He and the girl aid the conductor on two occasions, saving both the Polar Express and its precious always-on-time record. Throughout it all, the boy doubts remain, including the implication that he is just having a dream.
Even after reaching the North Pole, their hijinks continue, with all four children, some for better reasons than others, find themselves in the innermost workings of Santa's operation, watching as the elves finalize the two lists and wrap all the remaining gifts to go inside Santa's bag. Set down safely after nearly falling off a mountain of wrapped gifts, all the children await the midnight meeting with Santa, but as he moves among the crowd, the boy can only seem to sense him in the vaguest manner, until he allows himself to believe. To his delight, he is given a ride in Santa's sleigh itself and the first gift of Christmas - which he chooses to be a bell from the sleigh. Returning home on the Polar Express after a grand celebration of a successful sleigh launch, the boy bids goodbye to his new friends one by one when he gets home.
When he awakens on Christmas morning, he seems to decide that, even if the trip had been a dream, it was one he would choose to believe in. To his horror, the robe-pocket he put the bell in had a hole, but Santa made sure it was delivered in a wrapped box with a reminder to fix the hole.
As an adult, he narrates that while his parents could never hear the bell ring, and at one time most of his friends could do so, as years passed, it fell silent for all of them and even his sister, Sarah. Though he has grown old, it still rings for him as it does for all who truly believe.