The setting is Paris in the spring of 1968, amidst student protests. "Matthew," portrayed by Michael Pitt, arrives from America and connects with the brother-and-sister pair, “Theo” (Louis Garrel) and “Isabelle” (Eva Green), who share his passion for movies. They extend an invitation to their house for dinner while their parents are away. It quickly becomes apparent that these two siblings have a peculiar closeness—nothing overtly forbidden, but certainly intense. What follows finds "Matthew" drawn into their unrestrained activities – a combination of intellectual and physical exploration driven by curiosity, desire, and expensive wine. Bertolucci’s approach to using sex (and the film is abundant with nudity and sexual scenes) as a means of examining these three young, attractive individuals is quite distinctive, pushing boundaries and questioning their beliefs in a way that's meant to be unsettling. I wasn’t convinced throughout that the student demonstrations had much relevance to what was unfolding; it seemed like an attempt to give some intellectual weight to a story that often felt flimsy and primarily consisted of what could only be described as soft-core pornography. There are moments when it is genuinely shocking, but the characters feel underdeveloped; Garrel in particular seems largely passive, gradually showing his displeasure at the sexual connection forming between his sister and the visitor. It's not a successful film, though it’s undeniably bold, and might signify the conclusion of imposing Victorian values on modern cinema.

Source on TMDB