Powell's company, Four Star Television, produced the TV series, which premiered on CBS but was later telecast for its last year on NBC. David Janssen starred as Diamond, a hard-boiled private detective in the film noir tradition. His secretary, Sam, was shown only from the waist down to display her beautiful legs. Initially, these were the legs of Mary Tyler Moore, but later, the legs of other actresses were seen. Russ Conway appeared occasionally as Lieutenant Pete Kile during the final season. At one point during the three-year run, the show's setting was moved from New York City to Los Angeles.
Original music by Frank De Vol included the theme for the first and second seasons. The third season featured a jazz score by Pete Rugolo, including a new theme. The final theme was by Richard Shores.
Guest stars included Chris Alcaide, Phyllis Avery (three times), Francis De Sales, Don Keefer, and Joyce Meadows.