So Long At The Fair (1950)

It is 1889 and Paris is crowded with visitors for it is the eve of the opening of the Great Exhibition . Victoria (Jean Simmons) and her brother, Johnny (David Tomlinson), arrive to take part in the event. Leaving her brother at the bar Vicky retires to her hotel room for the night. Next morning she excitedly runs to see Johnny and is bewildered to find that both her brother and his room has disappeared. Her surprise turns to concern when all the other staff and guests deny ever seeing her brother. None of the authorities will believe her story, but by chance she meets a young English artist, George (Dirk Bogarde) who knows her story to be true. Together they must try to unravel the mystery.