Lionel Barrymore is pitted against his brother John in a comradeship of rivals as the Parisian police chief Guerchard and the debonaire Duke de Charmerace. Just who is the mysterious scoundrel Arsene Lupin remains in question until a good halfway through this first of several films devoted to the elegant antics of the wily French thief (Melvyn Douglas played the title role in Arsene Lupin Returns, 1938). The brothers strike sparks of biting wit off one another in their first film together, an elaborate plot that includes the theft, no less, of the Mona Lisa from the Louvre.