A Girl's Best Friend. Jim Nash Adventures, #10

Jim has a brand new Private Investigator's license, but he can't use it in Nassau. After a briefing in the Big Apple on the diamond market, he heads off to the sunny paradise to try and dissuade a friend from flashing a blue diamond at one of his infamous parties. Minus a guest list for the forty partiers, they're all suspects in the investigation until Jim finally realizes that a woman he knows could be the prime suspect.