The Great Jewel Robber is based on the true story of Gerard Dennis, who during a 12-month period managed to steal more than a million dollars' worth of gems. As played by David Brian, Dennis is an incorrigible ladies' man, who uses women to help him pull off his heists. The first of his conquests, played by Claudia Barrett, pays for his escape from the Canadian authorities. The second (Perdita Chandler) is his partner in crime in Buffalo, New York. The third woman in his life, played by Marjorie Reynolds, ultimately brings about his downfall. For the sake of verisimilitude, Mayor Stanley Church of New Rochelle, Connecticut (where Dennis was finally caught) appears in the prologue as himself.