The mother-daughter scene
Kills me every time I watch it, when she asks how making love feels like, because she knows she'll never experience it. Jane Alexander's monologue is superb, and Roxana Zal's body language says it all.
Jane Alexander really shines in this, even if I've read in some other places that her Oscar nomination was unworthy and came as a big shock, she was the heart and soul of the film and carried it outstandingly. She would have certainly won an Emmy had it been broadcast on TV as it was initially conceived.