The film was based on Nightmare in Manhattan, an Edgar-winning novel by Thomas Walsh.
Sydney Boehm's script for the film version was nominated for an Edgar in the screenplay category.
Aside from changing the setting from New York City's Grand Central Station to Chicago's Union Station (though the Los Angeles Union Station was the actual filming location), and changing the kidnap victim from a little boy to a blind, teen-aged girl, the script was quite faithful to its source material.
Union Station is a realistic 1950 film noir police and public nuisance kidnap movie starring William Holden, Nancy Olson, Jan Sterling and Barry Fitzgerald. It was released after Sunset Boulevard so by the time it came out, Holden had actually moved up another level of stardom. William Holden and Nancy Olson also appeared in Sunset Boulevard the same year.