Diamond's reputation is on the line and he's intense in his single-minded approach to finding a stolen gem. He was paid a day's fee for safeguarding a diamond necklace while it was on loan to a fashion model modeling it for a TV show. When he goes to return it, it's discovered that the diamond is fake. The Beverly Hills jeweler who supplied the gem berates Diamond, blaming him for the theft. The local police tell him it's out of his hands and warn him not to try anything on his own or they'll yank his detective's license. After he uncovers a clue from the model's roommate, he goes undercover at a casino, the Onyx Club, to continue his investigation. His tough guy routine lands him a job at the casino although it earns the wrath of a jealous co-worker. He romances the girlfriend of the casino owner to see what she knows about the model and the stolen gem.
David Janssen as Richard Diamond is handsome, masculine, fit and tough. His laconic coolness is featured magnificently in this episode which kind of has a mini spy movie-like quality to it. He looks great in a suit and Marcia Henderson looks great dressed up in fancy evening wear as the moll. There's a suave elegance to David Janssen and he's a pleasure to watch.