I was watching Prisoner of Azkaban tonight and had a little revelation.
In 2004, J.K. Rowling said, "[Alfonso Cuaron] put things in the film that, without knowing it, foreshadow things that are going to happen in the final two books. So I really got goosebumps when I saw a couple of those things, and I thought people are going to look back on the film and think those were put in deliberately as clues."
I predict the foreshadowing is when Lupin and Harry are talking and Lupin says, "You know the very first time I saw you, Harry, I recognized you immediately. Not by your scar, by your eyes. They're your mother, Lily's. Yes, oh yes. I knew her. Your mother was there for me at a time when no one else was. Not only was she a singularly gifted witch, she was also an uncommonly kind woman. She had a way of seeing the beauty in others even more perhaps. Most especially when that person couldn't see it in themselves."
We'll see if I'm right soon!