==comment==I posted this and now I have to add a comment....
I have never seen this movie. In fact, I never knew it existed. But I read the book (it is written by Evan Hunter). I bought it at Kennedy Airport on my way to Italy (high school trip) in 1971. I remember being very disturbed by the book and asked my English teacher about it, and he said, "Yeah, well that's what you get for buying books at the airport."
I am not sure I even knew until today this movie existed. And it sounds like it was filmed within yards of my house (my house was on the creek where the Fire Island ferries docked). Amazing....
L