Strangers on a Train (1951) brought Alfred Hitchcock back to box office success after the lull that followed Notorious (1946), and today it remains a favorite with the auteur's fans. Hitchcock presents a deliciously twisted thriller in this tale of murder and blackmail, with Farley Granger returning after his performance in Rope (1948) for a second outing with the director, but it's the creepy appeal of Robert Walker that makes Strangers on a Train such a macabre delight. There's nary a blonde in sight, but Ruth Roman, Laura Elliott, and Hitchcock's daughter, Patricia, all give memorable performances as the younger women, while Marion Lorne and Norma Varden provide some delightful comic relief in their smaller roles.
Granger plays tennis star Guy Haines, who meets a fan named Bruno Antony (Robert Walker) while on a train. Bruno knows all about Guy and his personal problems, especially that Guy can't be with his new love, Anne (Ruth Roman), until his wife (Laura Elliott, aka Kasey Rogers) gives him a divorce. Bruno proposes to kill Guy's wife while Guy kills Bruno's hated father, but Guy doesn't take him seriously until it's too late. When Guy refuses to commit Bruno's murder in return, Bruno sets out to frame Guy for his wife's death, forcing Guy to dodge the police and resort to drastic measures.
Like a lot of Hitchcock's protagonists, Granger's Guy quickly finds himself deep in a situation beyond his control, and the stress pushes him outside the comfortable norms of polite behavior. He becomes secretive, driven, and tense, but we get hints of his inherent darkness early on, when he argues with his faithless wife and then tells his girlfriend that he could strangle the uncooperative woman. Guy never seems especially upset that his wife is dead, just unhappy that he's the most obvious suspect. Granger is solid in the role, but the real star of the picture is Walker, whose talkative, unstable Bruno drives the action throughout. He's a weirdly likable killer, devoted to his mother and rather desperate for Guy's approval, and he's shaken enough by the act of murder to develop a kind of PTSD in response to it. Bruno's scenes with his mother and Mrs. Cunningham, played by Marion Lorne and Norma Varden respectively, show his ability to endear himself to older women through his "naughty" sense of mischief; in some ways he's the opposite of Joseph Cotten's homicidal Uncle Charlie in Shadow of a Doubt (1942). The role ought to have been a comeback moment for Walker, who had struggled with alcoholism after being left by his wife, Jennifer Jones, but the actor died tragically just months after finishing the film.
Hitchcock engages in his usual visual tricks to crank up the suspense, and the amusement park setting of the murder gives him with plenty of striking images to use. Bruno pursues Miriam Haines through the Tunnel of Love in a boat named for Pluto, the god of the underworld; she constantly looks back at him as she romps through the carnival, never recognizing her seeming admirer as a figure of Death. We see Miriam strangled in the reflection of her own glasses, and afterward the glasses worn by Barbara (Patricia Hitchcock) cause Bruno to relive the murder, complete with echoing carnival music and a spinning sense of vertigo. A thoughtful viewer might pause a moment to wonder why Hitchcock would cast his own daughter as someone the antagonist wants to strangle every time he sees her, but the scenes are certainly provocative. The director also has fun with the tennis matches, where the spectators watch the back-and-forth between the players just as we watch the deadlier match being played by Bruno and Guy. The climax, back at the amusement park, delivers a hair-raising finale on a runaway carousel, as well as a wonderfully vicious little scene in which Bruno loses the cigarette lighter that he needs to frame Guy.
Strangers on a Train picked up only one Oscar nod, for Best Cinematography, but it's certainly a picture every Hitchcock fan should see. The director followed this film with I Confess (1953), Dial M for Murder (1954), and Rear Window (1954). You can see more of Robert Walker in Since You Went Away (1944), Thirty Seconds Over Tokyo (1944), and The Clock (1945), while Farley Granger has memorable roles in They Live by Night (1948), Side Street (1949), and Senso (1954). Look for Ruth Roman in The Window (1949) and The Far Country (1954). Patricia Hitchcock, who is still living at this time, appears in two other Hitchcock films, Stage Fright (1950) and Psycho (1960), and she acted in numerous episodes of the Alfred Hitchcock Presents TV series.
PS - If you want to know more about Robert Walker, you can read a thorough discussion of his life and career at The Lady Eve's Reel Life.