For those who doubt...
...the greatness of this neglected noir, here's a spot-on appreciation of it (and the unappreciated Wendell Corey) from the Film Noir of the Week blog site:
http://www.noiroftheweek.com/2006/03/file-on-thelma-jordon-1950.html
Here's another:
http://www.popoptiq.com/the-file-on-thelma-jordan/