Something I just realized (SPOILERS)

When Walter McGinn is speaking with Warren Beatty in his fleatrap room, and says "You can offer us more than any ex-FBI agent ever could," I finally realized, after seeing this great film many, many times, that's when Parallax was saying that they were onto Beatty. McGinn was referring back to the Kenneth Mars character, who operated the train ride at Griffith Park, who was an ex-FBI agent helping Beatty out. So subtle and clever.

RIP to Lorenzo Semple, Jr., PARALLAX's co-screenwriter, who passed today at 91.