Purple Noon

Purple Noon is a 1960 Rene Clement film, an adaptation of Patricia Highsmith's book The Talented Mr. Ripley. It's fairly faithful to the book, which might accurately be subtitled Character Study of a Psychopath.

I watched it via Hulu, but it's behind their paywall now. The trailers I've seen give away too much of the plot, so I won't embed one here.

Slant Magazine calls it "a French macaroon full of arsenic". The Guardian gives it 4 out of 5 stars and praises the lead actor's performance saying, "Delon's Ripley is a Dorian Gray portrait of male beauty and unscrupulous daring, untroubled by conscience."

DVD Talk concludes:

A lushly picturesque tale of identity crisis, inferiority complex, emotional tug-of-war, and disguised resentment, René Clément's Purple Noon (Plein soleil) is a paradoxical film whose particular mixture of ingredients is not quite like any other.
...
The result is something uniquely unsettling, a murder-mystery in which the murderer is really the sympathetic, "relatable" one, with his dark machinations played out for our riveted delectation under a cloudless, idyllic Mediterranean sky -a seductive nightmare in broad daylight. It's as ravishing, entertaining, and aesthetically/narratively skilled as you could hope for, with a career-making star turn by the impossibly beautiful Alain Delon that will surely captivate and/or arouse anyone who lays eyes on it until the end of time.

Roger Ebert gave it 3 out of 4 stars and has a thorough plot description. Rotten Tomatoes has a critics score of 100%.