You want Hitchcock classics, we give you Hitchcock classic in all of it convoluted glory. In this one, two men each have a problem. Guy wants to lose his wife, Miriam, and marry Anne. Bruno wants to kill his dad. It just so happens that the two are on the same train.
Since Guy is a famous tennis player, Bruno is familiar enough with Guy's situation to propose the perfect murder plot. Guy doesn't take him seriously, but Bruno doesn't realize that and proceeds with his plan to murder Miriam.
After fulfilling his part of the deal, Bruno expects Guy to hold up his end. Guy is faced with a choice - to kill or not to kill. But as the cops close in on him for Miriam's murder and Bruno gets closer to Anne, Guy realizes he might not have a choice after all.