All I remember about this movie was I was very young (early to mid 70’s) and there was a woman who was set up a trip cord, and a young boy ran from her, but tripped on the cord, knocking him out.  She then filled up the tub and drowned him.  As she drowned him, she saw in his place a baby playing in the  bathtub, superimposed memory of the drowning child.  She was obviously insane, and I remember my mother heard the music or the audio from the movie as she was in the other room and she made me turn it because it would give me nightmares, which of course she was right..thanks