This 1956 movie, presented right after the Joe McCarthy Communist witch hunts, and at a time when America still was terrified of being infiltrated by Russian spies and sympathizers (oh, remember what a quaint era that was?), remains one of the best movies about properly motivated paranoia ever made. (For others, see All the President’s Men, The Parallax View, The Thing, and Alien, to name a few.) Don Siegel, who eventually directed Clint Eastwood in Dirty Harry, directs this still-scary story about people being changed, one by one, in ways that are very sinister, but not immediately apparent…