I am sorry to be a party-pooper, but I don't care for "Double Shock". I am a BIG
fan of Martin Landau from Mission: Impossible (and it was there, in the episode "The Mind of Stefan Miklos" which is considered one of the finest in the series) that Landau (as Rollin Hand) impersonated two people with entirely different personalities). What bugs me about this one is the nasty housekeeper played by Jeanette Nolan (who is actually a fine actress) but her character really gets on my nerves.
It is good that Landau turned down Mr Spock, because he is ten times the actor Leonard Nimoy is..emotionless Spock was perfect for the one-dimensional Nimoy, whereas Mission Impossible gave Landau the opportunity to play a very wide array of characters, something that Nimoy really isn't good at.
I keep expecting Jeanette Nolan to completely flip out, start cackling and turn Columbo into a frog or something. "Night Gallery" fans will understand.
I agree with your analysis YM but you did fail to mention one redeeming feature of this ep....
the yummy Julie Newmar.