This Is Probably the Best Film of All Time
It out-wits "Chinatown," which it greatly resembles, by a country mile. It deals with human evil in a way that my perennial film favorites ("The Best Years of Our Lives," "The Sound of Music") don't. I just re-watched it and realized that the film is misleading because Martha is not only not the lead character, she's not even close to being the lead. First is Sam. Second is Walter. Third is Toni.
Martha really is a distant fourth. She is what her two men react to and change in relation to, and therefore what Toni reacts and changes to. Two things jumped out at me in a way they hadn't previously. First, Sam's revelation that he never even saw what froze Martha in time all those years ago and arranged her destiny. Second, Walter's revelation that Martha has been promiscuous, of which the viewer is kept totally ignorant until the climax. There's so much of Martha the viewer never gets to see, because the truth is that the film is not about her; it's about her effect on others.
She is insane and comes very close to destroying Sam (and Toni).