The young lady playing the wife is Sarah Marshall her father was a famous actor and a war hero. She comes from a long line of famous British actors and writers. She is related to Mary Shelley who wrote Frankenstein for example.
This was actually the penultimate (next to last) episode, but given the storyline here, it would have better served as the series finale. I do like the original opening theme being played - these are cut off because there is an announcer who says "The Donna Reed Show" as the theme ends. In syndication, they used the closing theme as the opening theme.
I can see where this should have been the last episode broadcast. Paul Petersen should have had the last line, which would go something like this: "Well here we are in the same old house, stuck in sitcom land forever."
Trisha looks so much like her adopted brother, Jeff. Perhaps she was Alex’s illegitimate daughter from a secret affair! And he schemed to present her as an orphan the family needed to adopt.