There's a great scene about 3/4s of the way into Alfred Hitchcock's Strangers on a Train where Guy's girlfriend (played by Ruth Roman) goes to talk to Bruno's mother about her son being, you know, a psychotic murderer - it's probably the only really good scene involving Ruth Roman's character actually, who's pretty forgettable as the standard bearer of heterosexuality inside a very queer film.
It's okay, Ruth - you never really stood a chance against the fiery chemistry between Farley Granger & Robert Walker. Not many would've. Anyway I never noticed until watching the film over the holidays that the scene takes place in the library! And Hitch hilariously shoots Bruno and his mother exiting the room in the exact same way.
What a pair of queens. I do want to give a shout-out to Marion Lorne (who's probably best known for playing Aunt Clara on Bewitched) who makes Mrs. Antony's cluelessness both very very funny and totally creepy all at the same time - there are a great many Great Mothers in the Hitchcock Canon and she's right up there.