A young American exchange student, Matthew (Michael Pitt), has come to Paris in order to study French. Though he has lived there for several months, and will stay in Paris for a year, he has made no friends. As a huge fan of film, he spends most of his time in the Cinmathque Franaise. Eventually he forms a rapid friendship with a Frenchwoman, Isabelle (Eva Green), and her brother, Tho (Louis Garrel). Isabelle and Theo claim to be twins originally conjoined at her right and his left shoulder, although as they are opposite sexes this cannot be possible. However throughout the film, scars on their shoulders can be seen. All three have an avid love for movies, especially "the classics". As their friendship grows, Matthew learns of the extreme intimacy shared by the siblings (what one reviewer described as "incestuous in all but the most technical sense") and gets pulled into their world. Over time he falls in love with them, and the three seclude themselves from the world, falling further and further from the reality of the 1968 student rebellions. An abrupt ending to this relationship comes when that world is shattered and they are compelled to face the reality of 1968 France.