"Les Diaboliques" has one of the best plots you will ever find in any mystery or suspense thriller. The excellent directing, acting, and writing combine with the story itself to make it a memorable experience.
If you enjoy quality mysteries or thrillers, you will almost certainly enjoy this one - and if you have not seen it yet, you might just want to buy or rent it now, before you read any more reviews. This comment will avoid any discussion at all of the actual plot itself, because the less you know in advance, the more you will enjoy it. The few implausible elements in the story do not detract at all from the enjoyment.
A great plot does not all by itself make a good movie, and everything works especially well here because of the expert pacing by director Henri-Georges Clouzot and good, mostly understated acting by the main actors. We are drawn into their world very nicely. Everything about the characters and events is built up perfectly, to give the brilliant climax its full effect. Once again, see it before you find out any more.
Even if you do not normally watch black-and-white films or foreign movies (this is in French), if you enjoy thrillers, watch "Les Diaboliques" as soon as you have the chance.
