Synopsis by Hal Erickson
Finding his hereditary title to be a detriment, Grand Duke Augustus Peter (Theodore Roberts) adopts the pseudonym of Mr. De Grex. In this guise, he "whoops it up" at the gambling resort in Monte Carlo. The plot (what there is of it) thickens when Grand Duchess Fedora (Dorothy Davenport) finds herself ardently pursued by such erstwhile Romeos as American visitor Richard Lane (Carlyle Blackwell) and Britisher Lord Huntersley (Frank Elliott). The trade magazine Variety felt that the strength of the film rested in the performances of its character actors, and the nominal hero Carlyle Blackwell failed to sustain interest in his portions of the story. Like many films of its era, Mr. Grex of Monte Carlo was based upon a Saturday Evening Post serial.