Created by Jack Webb, the concept of Dragnet was very simple. Two cops, Joe Friday (Jack Webb) and Bill Gannon (Harry Morgan), investigate a crime. Much of the story is told in voice over narration by the main character, Joe Friday, who filled in details and explained the action.
In some respects, this was a realistic show detailing the leg work that goes into a police investigation. It depicted the mundane routine that make up most of a police officer's work.
The partners looked at evidence, questioned witnesses and suspects and consulted with experts. There was very little violence in the series (I'm not sure a shot was ever fired by either officer) and few chases and yet it managed to hold an audience's attention.
The show could be preachy and obvious at times, but overall, it remains one of the best police dramas ever to hit the airwaves.