Forget Hitchcock, and enjoy this film on its own merits. Never mind that it has elements of other films since...Color of Night, So I Married an Axe Murderer, Fatal Attraction, et al. Even a little of Play Misty for Me. You're going to be manipulated, you're going to know that you are being manipulated, and you go along for the ride anyway, thinking she did it, but then maybe that's what I'm supposed to think so maybe she didn't do it...but then they'll think I'm going to think that so maybe she did do it after all..and in the end you decide just to wait and see.
Roy Scheider is brilliant in just about everything he does, and Meryl...well, she literally takes your breath away when she walks through the door for the first time. I've never seen her looking more beautiful. And she plays it with the same qualities of Tippi Hedren in both The Birds and Marnie, the same qualities she had in Kramer vs Kramer...nervous, flawed, a bit bewildered, an innocence that is belied by past guilt. Roy's character finds himself atttracted to her even though he's afraid of what he might discover as he digs deeper.
Joe Grifasi isn't as clueless as other reviewers have indicated, but you're pretty certain you know what happens to him, if you've seen Fatal Attraction.
So...think about all of the Hitchcock elements, all of the afore-mentioned movies after you've watched it, or better yet, watch it again and look for them.
It's a nice little psychological thriller, much like others, but still very enjoyable.