Adaptation Displacement: Many people aren't even aware it's based on a novel. Even though he was a prolific writer of crime fiction and true crime, Arthur La Bern is largely forgotten except for having his book Goodbye Piccadilly, Farewell Leicester Square turned into this film. Ironic, since he loathed the film.
Complete Monster: Bob Rusk, despite his veneer as a kind-hearted, jovial, and upstanding citizen and good friend to Richard Blaney, is in actuality a sexually sadistic psychopath who moonlights as the infamous "Necktie Murderer". Rusk rapes and then strangles his female victims with his tie, proclaiming that "all women are the same" and denouncing them for not fulfilling his perverse urges. Revealing his true colors to Richard's ex-wife Brenda, Rusk forces himself on her before violently strangling her to death. Rusk later lures Richard's lover Barbara to her death, and uses the dead woman's clothes to frame his old friend for the murders. When confronted by Richard and Chief Inspector Oxford, Rusk is in the process of disposing of the corpse of yet another victim. Completely bereft of compassion and remorse, Bob Rusk is only able to mask his true self with superficial charm, and deep down is an utterly callous and twisted individual who kills for his own pleasure.
Genius Bonus: Not only does someone comment "We haven't had a good, juicy series of sex murders since Christie", the basic storyline is almost identical to the John Christie case: a Faux Affably EvilSerial Killer successfully frames an acquaintance, but the police belatedly start investigating him.
Clive Swift plays a Henpecked Husband eighteen years before he was Richard Bucket, such a prime example of that trope that he's the picture example at the top of the page.
Relating to the politician's speech at the start of the movie, the Thames has been cleaned up a lot since 1972.
Jerkass Woobie: Richard Blaney, he's definitely a mean person, but is Wrongly Accused of being the Necktie Killer and lost the two women in his life who understood him, Brenda and Babs, to the real killer - his own friend Rusk.
Narm: The tongue sticking out. Apparently meant to accentuate the horror of the scene, but it just looks comical. But given who the director was and the Black Comedy elsewhere in the film, this might be the Intended Audience Reaction.
Spiritual Successor: It mixes two of Hitchcock's frequent recurring storylines — a Serial Killer is on the loose, and a wrongfully-accused man seeking to Clear His Name is forced to go on the run. Kaleidoscope, his aborted Serial Killer film that evolved into Frenzy, was originally conceived as a prequel to Shadow of a Doubt, and Rusk, as a charming man who's also on a killing spree, definitely has similarities to Uncle Charlie from that film, as well as a few hints of both Bruno Antony and Norman Bates. The title—a six letter, two syllable word connoting madness—also sounds like it was meant to evoke Psycho.
Unintentional Period Piece: It was filmed at Covent Garden when the place was still a very busy fruit and veg market, not the tourist attraction it is today. Perhaps averted, given that Hitchcock, the son of a London market porter, was well aware that the market was due to close in a few years.
A humorous one occurs when Oxford's wife suggest an alcoholic drink for Spearman recommending a margarita — a cocktail that Spearman has never heard of. When she describes it, both Spearman and Oxford look flabbergasted by her description of the drink (and, of course, neither of them picks up on her mispronunciation of "tequila"). The humour comes from how she discovered it from her exotic cooking class and it seems like such a weird drink — but these days, margaritas are a very common alcoholic drink everyone knows about.
", the basic storyline is almost identical to the John Christie case: a Faux Affably Evil Serial Killer successfully frames an acquaintance, but the police belatedly start investigating him.