Paul Meurisse plays Michael Delassalle, a school principal who is disliked by both his wife (Christina, played by Vera Clouzot) and his mistress (Nicole, played by Simone Signoret). They dislike him so much that they plot together to kill him. But the murder is the easy part. Things start to unravel when the body disappears, an unusual turn of events that puts even more strain on the weak heart of Christina, gives both women reason to mistrust one another, and creates quite the atmosphere of unease at the school.
Directed by Henri-Georges Clouzot, who has more than one masterpiece in his filmography, this is about as wonderful and twisted a thriller as you can get, with just a tinge of the supernatural to allow it to have one toe dipped in the horror genre (anyone in any doubt about that just needs to remember the final scene). Clouzot is an expert at creating tension, with a number of scenes here akin to a tightened spring, going and going until you just know that it will snap uncoiled at any moment.
The script, adapted by Clouzot and Jerome Geronimi, with some input from others, from the novel by Pierre Boileau and Thomas Narcejac, is judged to perfection. Characters are set up quickly in the opening scenes, motivations are established, and then it's on to the more dastardly work, when things start to alternate between that tension and a certain amount of playfulness. Even the finale manages to provide explanations without feeling as if everything has stopped just for the sake of exposition, meaning that not one moment of the (approximately) 90-minute runtime feels unnecessary or wasted.
Mesdames Clouzot and Signoret are both fantastic in the main roles, the former constantly pained and strained while the latter tries to keep her cool in the face of a situation growing ever more improbable and stressful. Meurisse, despite not actually being on screen in non-corpse form for too long, also does a great job, enjoyably delivering lines of dialogue that show just how callous and unlikable he is. There are some other memorable characters here, but Charles Vanel is the main standout, a policeman who offers to help a distraught Christina after she has been to the morgue to identify a body she assumes will be her "missing" husband.
There may be modern movie viewers who watch Les Diaboliques and find themselves looking out for twists and turns, confident that they know how things are going to pan out and feeling as if they've seen it all before. I would ask those people to not do that. Don't try to second-guess the film, just sit back and enjoy it all. Yes, it may do some things that will feel familiar, but this is a film from the mid-1950s, meaning most of the other films that you have seen covering similar territory have most likely been influenced by this. And it's a damn fine film to be influenced by.
There's a lovely edition of the film here.
Americans can buy it here.