Director Fritz Lang was attracted to the British period piece Moonfleet because of the relatively unregenerate nature of its greedy "hero" Stewart Granger. Young Jon Whitely, who is in the legal custody of Granger, learns that he is to inherit a valuable diamond. Hoping to get his own hands on the gem, Granger packs Whitely off to boarding school, but the boy returns to bollix up his guardian's plans. Just when it appears that a cynical ending is on the horizon, Granger does right by Whitely. Adding spice to Moonfleet are George Sanders and Joan Greenwood as a wittily decadent aristocratic couple. Lang's first CinemaScope effort, Moonfleet was based on a novel by J. Meade Falkner.
~ Hal Erickson, All Movie Guide