There can be a small study made of movies set in Worlds Fairs. Start with THE GREAT TRAIN ROBBERY, where a few scenes appear at Joseph Paxton's Crystal Palace. Then CENTENNIAL SUMMER, where the 1876 Philadelphia Centennial Exposition is the center piece. Go on to The STARS AND STRIPES FOREVER, where Clifton Webb (as John Philip Sousa) performs at the 1896 Cotton Exposition in Atlanta. Then go to this film, followed by MEET ME IN ST. LOUIS (the St. Louis Worlds Fair in 1904). There would be others.
SO LONG AT THE FAIR is about the Paris Worlds Fair of 1900. It is based on an incident that has grown into a modern urban legend concerning how a young woman was told that she had no mother (or,in the film, a brother), there was no room in a hotel that she left this party in, and that she has been imagining events and people for the last couple of days (at least). In the original legend, the young woman is so hopelessly lost by this she loses her mind and is put into an asylum. In the movie (and its novel and other versions) eventually the massive conspiracy to cover-up what happened is revealled.
Did it happen? Did a young woman (here played by Jean Simmons) come into Paris, readying itself for the big world's fair, find herself confronted by a conspiracy that claimed she imagined it all? No historical evidence has ever surfaced that this actually happened. Yet the story survives. It is a terrific story, for it is based on the fragility of reality. If everyone doubted us how could we prove what we said was true? Hard to say. You need some people to validate your story in part or whole for people to believe you. In all the retellings of this story, the heroine is isolated once the mother or brother is gone. The very person to prove the story is the person whose absence is deplored but questioned.
As a costumed historical film, SO LONG AT THE FAIR is very good, with Simmons aided by Dirk Bogarde as the one person in Paris who believes her. And together they prove that Cathlene Nesbitt (the hotel owner) is lying - but with powerful friends to assist her.
It is not the best retelling of the story - Hitchcock used the plot, but changed it, in THE LADY VANISHES, where it is the missing spy, Miss Froy, whose existance is questioned by all who hear the heroine (Margaret Leighton), except Michael Redgrave.
I should add that students of this mystery don't know which world's fair is the site of the story: the 1889 French fair (where the Eiffel Tower first appeared), or the 1900 one. However there was also the 1867 fair in Paris, where Tsar Alexander II of Russia arrived. One version of the story tells that the reason for the cover-up deals with an attempt on the life of the Tsar. So it could have been one of three fairs that was the basis for this marvelous yarn.
