4. Strangers On A Train (1951)
In what is likely one of the best set-ups for "a perfect murder", Strangers On a Train focuses in on... um, two strangers on a train. While riding a train to give divorce papers to his wife, Guy Haines - a professional tennis player - meets Bruno Anthony, a man who recognizes Guy from the tabloids, and as such is familiar with his marital problems. Bruno presents a unique solution: Bruno will murder Guy's wife Miriam, in exchange for Guy killing Bruno's father. They'll each have an alibi for the time of the murder, and there will be nothing connecting the two of them together, preventing either from becoming a suspect. As well thought out as Bruno's idea is, Guy rejects it. However, determined to see his plan through, Bruno goes ahead and kills Guy's wife. He then threatens to contact the police unless Guy carries through his murder. The brilliance of the film hinges not on the story (despite how clever it is), but rather Hitchcock's use of doubles and opposites, visually illustrating how similar and yet how different Guy and Bruno are. But it's especially important to play close attention to that, because then you'll catch the second mind-blowing thing about this movie, which is... If you watch it a second time, the movie totally changes
. Watching through it once, you see Bruno tries to force Guy into a murder scheme, but it fails because Guy is too good of a guy, blah blah blah. But on a second viewing, you see that Guy orchestrated the whole thing! He gets Bruno to commit the murder for him, then gets him turned over to the police. Guy gets his wife murdered, and gets away with it scot-free
! The hero of the film becomes the villain!