Strangers on a Train (1951)

Farley Granger plays Guy Haines, a tennis star who hates his estranged wife and wants to be free to marry another woman. On a train, he meets Bruno Anthony (Robert Walker), who hates his father. Bruno has a chillingly simple plan: each could kill the other's victim. No motive, no clues, nothing to link Guy and Bruno but a casual meeting of strangers on a train. Guy laughs it off. But soon, his wife is horribly murdered. And Bruno shows up to demand that Guy keep his part of the bargain.

Strangers on a Train is one of Hitchcock's most diabolical thrillers; a tale of dreadful possibilities twisted tightly with nerve-wracking suspense and macabre humor and brought to a spectacular conclusion aboard a merry-go-round spinning wildly out of control.