John Barrymore meets his brother Lionel in a comradeship of rivals. One plays the debonaire self-styled Duke of Charmerace, the other, Paris police chief Guerchard. Just who is the master burglar and professional scoundrel Arsène Lupin remains in question until a good half way through this first of several films devoted to the elegant antics of the wily French thief. The clever script and direction keep the acts of larceny, grand and petit, off screen, conveyed to us through indirection and inference. Featured screenwriter Lenore Coffee was a renowned Hollywood "script doctor" who among other things had mastered the art of dialogue years before sound. Arsène Lupin also offers a chance to see Karen Morely as the mysterious Sonia, a parolee in the service of les flics, whose love affair with the light-fingered boulevardier is as hot as the times would allow, and then some. Morley, a woman screenwriter's dream of a plucky personality, later was blacklisted.