Based on a lugubrious novel by Ludwig Wolff, The Mysterious Lady is a romance/espionage tailored to the talents of Greta Garbo. The divine Miss G plays an alluring Russian spy, directly answerable to satanic-featured general Gustav von Seyffertitz. While she's accustomed to fomenting suicides and apoplexy amongst her male victims, Garbo cannot help but become romantically involved with Austrian-officer Conrad Nagel. Forced to choose between her love of Russia and her love for Nagel, Garbo decides upon the latter--meaning that there's a bullet in the future for vonSeyfertitz. For all its MGM gloss, Mysterious Lady would be just so much borscht without the ethereal presence of its female star.
~ Hal Erickson, All Movie Guide