When the series later reran on late night TV I stayed awake as best as possible to catch the earlier episodes. Loosely and vaguely inspired by THE THIN MAN movies in which a detective's wife helped him solve mysteries against his better judgement as the two bantered back and forth. In this case, the "detective" happened to be the Police Commissioner of San Francisco.
The other major difference was that Susan St. James as Mrs. McMillan was far from the witty socialite played by Myrna Loy in the movies. A full 26 years younger than her TV husband, Sally could be somewhat ditzy. Fresh off of NAME OF THE GAME, St. James had both amazing and surprising chemistry with Hudson so the age difference never really seemed a factor either in the show or to viewers.
John Schuck, later known for his role as Herman in THE MUNSTERS TODAY and known as a Klingon in STAR TREK fandom had a generally small but plum role as the Commissioner's sidekick, Sgt. Enright for most of the series run.
Once Rock stopped trying to be hip, he also looked more like his classically handsome self and the two made for a gorgeous couple.
As part of NBC's rotating Mystery Movie "wheel" with McCLOUD and COLUMBO (and assorted others over the seasons), McMILLAN & WIFE's mysteries were quality productions, clever and generally done in "fair play" style where the viewers could themsleves look for clues.
Nancy Walker added a much-needed acerbic feel to the lovey-dovey couple as maid Mildred. Walker also appeared concurrently in RHODA and a series of popular TV commercials for paper towels and later would get several tries at her own series.
Sally was pregnant several times throughout her five seasons on the series, mainly because St. James was pregnant in real life. We never saw her have a baby but in later episodes one was mentioned but never seen. In a dispute, the actress left the show and her character (and presumably the baby) was said to have died in an airplane crash. Nancy Walker left around the same time, replaced on the show by Mildred's sister Agatha, played relatively straight (and more sedately than one would expect) by the legendary comedienne, Martha Raye.
At that point, the show was retooled as simply McMILLAN. Hudson started looking more his real age and as a widower was allowed some romantic interests. Without Sally, though, Mac seemed wearier, also. The mysteries were still top-notch and the guest stars were impressive as ever but something was missing. McMILLAN lasted only one season of its irregular episodes.