A con artist masquerades as Russian nobility and attempts to seduce the wife of an American diplomat.

Although she is the mastermind of a gang of crooks, Kate Westhanger's talents are unknown to those outside her circle, thus enabling her to infiltrate George Flanbaugh's gold syndicate. While ostensibly working for Flanbaugh, Kate actually is compiling information on a large gold shipment. One day, while working, Kate meets young criminologist Michael Pretherson, and although finding herself attracted to the sleuth, she laughs at his detective work and challenges him to stop her.

Although he has been appointed to guard the fortune of young Thomas Creighton, the unscrupulous Lord John Needham decides to spend all of it after Tom runs away. Then, however, an announcement comes that Tom is returning and that he plans to claim his money. Fearful of punishment, both from Tom and the authorities, John kills his cousin and exact double, Joseph Norbury, and takes Joseph's place, thereby making it seem as if the dead man is really John.