"On a train, wealthy, neurotic Bruno Antony recognizes tennis player Guy Haines and strikes up a conversation. While using Guy's cigarette lighter, Bruno notices it is inscribed "From A to G," and guesses that "A" is Senator Morton's daughter Anne, whom Guy intends to marry after Miriam, his current wife, divorces him. Over lunch in his compartment, Bruno describes to Guy his hatred of his father, and suggests a plan for a perfect murder. He proposes that two strangers, who each want someone in their life killed, swap murders. In that way, each has murdered a perfect stranger and is unlikely to be apprehended. For example, Bruno says, he could kill Miriam, and Guy would then return the favor by killing Bruno's father. Believing Bruno to be a harmless crank, Guy agrees that the theory is viable and disembarks from the train at his home town of Metcalf, unaware that he has left his distinctive lighter in Bruno's compartment. In Metcalf, Guy proceeds to the music store where Miriam works. There, Miriam tells him that although she is pregnant with another man's baby, she has no intention of divorcing him. In full sight of the other employees, a furious Guy brutally shakes her, then calls Anne and, still angry, shrieks that he would like to strangle his wife. Meanwhile, Bruno, at his parents' home, overhears his father threaten to institutionalize him, and decides to put his plan into action immediately."
Hitchcock is so good. He's the kind of good that, even when you've seen a film a couple of times, and have read a good deal about it, that you can go back to the film a few years later and still get swept up. And of course, he's a top-notch formalist, using images to not only tell the story, but to create emotional impressions that are not easily forgotten. It is this that truly gives the film an everlasting quality, like the shot of the murder reflected in the glasses or the sight of an out-of-control merry-go-round, that bastion of childhood safety for decades. Guy Haines never really acts like a killer, though I guess it could be argued that he was an accessory, but there sure is a lot of guilt to go around, he even addresses it directly in a conversation with Anne, and that guilt, and the possibility that he could actually do the deed bring this into the noir frame. Go see it if you haven't already.