I saw the beginning of what I think was a movie in the late 70’s on TV.  It was set near dusk, and this woman walked down to the beach in a swim suit alone.  From the cliff above her a group of bikers shines a headlight on her.  She freezes and starts to run away, but they catch up to her and pull her onto the sand.  Then another guy comes up, fights off the bikers one by one, and that’s when my mother made me turn off the TV.  What movie?  What else happened?