What I find more interesting about that is the idea that Mac apparently had an interracial relationship in the 60's. The show would have been made in 71/72, when interracial relationships were rare on US television.

I just watched "An Elementary Case of Murder" myself. It was really good. I would enjoy going and comparing and contrasting it to the IRONSIDE original.
The IMDb Trivia on the McMILLAN & WIFE episode page says this was an extra episode produced after the season had originally wrapped, so they must have had to scramble to find a script. I did notice that the appearances of Mac, Sally, Mildred and Enright were different: Mac's moustache looked fake and seemed to change between scenes, Sally's hair was less shaggy and she was of course pregnant (and thus relegated to the bench for most of the episode), Mildred had a shocking red 'do with a wild pompadour, and Enright looked like he was auditioning for Sha Na Na (didn't he know a dab'll do ya?).
All that said, everyone did an outstanding job and it was a compelling episode to watch. Interesting to see Mac doing some soul searching and perhaps admitting to himself that he allowed personal feelings to cloud his investigation. He is only a man, after all. Also interesting to see Sally plumb new depths of jealousy and to see Mildred go Mama Bear on Mac. If Mildred worked for Sally's mother, she may have known Sally since childhood, which would explain the over-protectiveness.
PS: For fans of other 1970's cop and detective dramas, I'm pretty sure the romantic getaway house on the bay was the same one used in a very early BARNABY JONES episode guest starring William Shatner.

That is so interesting. I went back and watched the Ironside episode, required for this huge perry Mason fan. One major thing - the acting in McMillan was SOOOOO much better. Anne Baxter must have been forced into her part on Ironside. She was really camping it up, since I know she was a decent actress.