Anything where some entity takes over your mind. That gets me every time, Betsy. Maybe that’s why the idea of dementia freaks us out. We’re losing the precious gift of memory. What gets into our heads when what defines us is gone? I know you asked me to stick to the 20th century—and I will—but just a quick reference to 1956’s “Invasion of the Body Snatchers.” They keep remaking it, so its terror applies to any time period. The title is a little off base since the body stays the same, but the mind is no longer calling the shots. Here are three movies that opened since 2000, one just this year, that I can’t watch without feeling my blood freeze.