The series often did well with exploring awkward social foibles and depicting (usually) Mary's attempts to navigate embarrassing situations.
This happens here when her father suddenly retires, and the parents move to Minneapolis - just around the corner from Mary's in fact. Soon they are watching Mary's every move and wanting to know where she's going, when she'll be home.
The parents are kind of annoying. Dottie (Nanette Fabray) can't stop with the 'people think Mary and I are sisters' angle and Walter (Bill Quinn) is a neat freak but never satisfied. (Rhoda's mother was annoying too, but funnier.)
Mary is seen returning from her date at 8.27 am the next day.