Humans are always Polygamous.

Rating: 10/10 (14 January 2020)

Man: "I never understood why you walked away (from medical studies)."
Friend: "It's a nice feeling. I do it a lot."
The "nice feeling" that the Man's friend, here, is referring to is perhaps, the Sense of Freedom that a man with No Attachments whatsoever, can enjoy without hesitations or boundaries...The Power to walk away from Commitments.
Right at the beginning, the social event where the Man (who is a doctor) and his friend meet each other after many years, is an Anonymous Party, where no one knows anyone and hence one could make willful choices of actions towards perceiving that illusive personal Happiness he/she is in the quest for. This Party could be an Allusion to that ideal place where one hides away from the others for a while and does what one desires for experiencing Happiness, and it could be some Flirtation, Sex or a seemingly harmless combination of Heroin and Coke ...or just a passion for playing a plain Piano.
The Man and his beautiful Wife, return from the Party, but only after having their Commitments for each-other seriously challenged, and they discuss, question and probe anything that defines any aspect of a marital/sexual relationship between a Man and a Woman. Love and Loyalty. Expectations. Jealousy. Wife's (illusive) desire for Security and Commitment, Human being's Polygamous Nature and the futile attempt to control it. The Wife even dreams of her subconscious desire to stray more and more away from the Man, mentally and physically.
Realizing that the Wife is not entirely faithful to him, the Man gets involved into adventures of his own. But will he be really as deceptive as one of the earlier lines in the movie says: "One of the charms of marriages is that it makes Deception a necessity for both the parties." ?
...Does their marriage survive this Storm ?
Watch it in Stanley Kubrick's 'Eyes Wide Shut (1999)'