Alternative storyline (SPOILERS!)

Can't help but thinking that if I had written the story, here's what we'd have found out at the end: Twenty years ago it was Carol (Diane Baker), not Lucy (Joan Crawford), who'd actually killed Lucy's husband and his lover; possibly because of some kind of Electra complex and jealousy. Lucy, being a fiercely protective mother, then takes the rap for Carol's crime, subjecting herself to twenty years of "therapy" in the psycho ward, which screws with her mind enough to make her sanity in doubt when the murders begin again. But it ends up being Carol all along who was, and is, an un-rehabilitated killer.