The story goes that a fellow told Alfred Hitchcock that after his daughter saw Psycho she refused to take a shower and that after she saw Diabolique she refused to get in a bathtub. Well, Hitchcock said, send her to the dry cleaners.
Diabolique is one of the most masterful scary movies you could hope to see. Even after 50 years, when the twist is probably well known, the movie is so well crafted and so well acted that it still carries me along. It takes place in a second-rate French boarding school for boys run by a sneering brute named Michel Delasalle (Paul Meurisse). His wife, Christine Delasalle (Vera Clouzot), who actually has the money in the family, is a weak woman with a bad heart, whom he abuses and humiliates. He openly has taken as a mistress a teacher in the school, Nicole Horner (Simone Signoret), whom he has smacked around one too many times. Christine and Nicole hatch a plan to lure Delasalle to Nicole's house some distance from the school. There, they will drug and drown him, then carry him back to the school and pitch his body into the unused, scum covered water of the school's swimming pool. When the body is discovered, it will be called a suicide or an accident. The two women pull it off...but when the pool is drained, there is no body. Then the suit Delasalle was wearing is delivered to the school by a laundry. A student is given a penalty and says it was the headmaster. A Delasalle appears to have registered at a local hotel. The two women don't know what is happening, and the strain begins to tell on them. They begin to bicker and blame each other. Nicole leaves the school. Christine must stay, but she is showing signs of emotional and physical collapse. Then the plot really begins.
So many elements, for me, really work. Everything in the film looks tawdry and worn. The swimming pool water is filthy and covered with slime. Every now and then small bubbles break the surface. The photography (and the film is shot in black and white) feature deep shadows, dark nights, candles. A shoe will appear, half hidden; a doorknob slowly turns; a bathtub looks like it could use a scrubbing. And there is no background music to speak of, just the quiet sounds of things moving and breathing. At the same time, the activities of the boys in the school are well developed and we come to recognize several of them. They bring us back a bit from the sense of something terrible happening, then we slip back into the movie.
Clouzot, in my opinion, has done a terrific job of building a sense of dread, but at the same time keeping us off balance by disguising what may be happening. Even though the "secret" of the plot is by now well known, Clouzot's craftsmanship keeps us (or at least me) watching. He spends whatever time he needs to build a scene or create an atmosphere. Watch how the serving of fish at the start of the movie is used to create whole stories about the school, the life of the boys, the situation of the teachers, and the characters of Michel Delasalle and his wife. Watch how Clouzot builds a creepy sense of dread when Christine goes to the morgue to identify what she thinks may be her husband's body. The sequence takes us from Christine trying to establish why she thinks the body is her husband's to the two attendants taking a cheap wooden casket from the basement of the morgue to the viewing room. At some point we realize that we are getting nervous ourselves about what might be in that box.
The end of the movie, when it was released initially in the United States, had people leaping three feet off their seats. That probably won't happen now to a new viewer, but the movie remains, in my opinion, a very fine piece of work.